Antiinflammatory effects of various drugs on acetic acid induced colitis in the rat

Luteolin peracetate and gossypolone inhibit immune complex-mediated neutrophil activation in vitro and dermal-epidermal separation in an ex vivo model of epidermolysis bullosa acquisita

Introduction

Natural products have been shown to an important source of therapeutics for human disease. In this study, we aimed to identify natural compounds as potential therapeutics for epidermolysis bullosa acquisita (EBA), an autoimmune disease caused by autoantibodies to type VII collagen (COL7).

Methods

Utilizing an in vitro experimental system, we screened a natural product library composed of 800 pure compounds for their inhibitory effect on COL7-anti-COL7 IgG immune complex (IC)-mediated neutrophil activation and on neutrophil-mediated tissue damage.

Results

Three natural compounds, namely luteolin peracetate, gossypol, and gossypolone were capable in inhibiting the IC-induced neutrophil adhesion and oxygen burst in vitro. Furthermore, luteolin peracetate and gossypolone were able to inhibit the anti-COL7 IgG induced dermal-epidermal separation in an ex vivo model for EBA.

Discussion

In summary, this study demonstrates that luteolin peracetate and gossypolone are potential therapeutics for experimental EBA, which deserves further investigation.

Anti-anaphylactic action of nordihydroguaiaretic acid in antigen sensitized guinea pigs

Therapeutic natural products and medicinal herbs has gained popularity. The anti-antigenic action of the plant alkaloid nordihydroguaiaretic acid (NDGA) was studied in ovalbumin (OA)-sensitized guinea pigs. In one series of experiments conscious, non-sedated guinea pigs were challenged with OA aerosol. Specific airway resistance (SR_AW) was monitored using a two-chambered whole-body plethysmograph. OA aerosol increased SR_AW above that produced by vehicle administration. Prior NDGA administration by a 1min 0.9% aerosol (w/vol) attenuated the increase in SR_AW resulting from OA challenge. In the anesthetized guinea pig pretreated with indomethacin, pyrilamine and propranolol, intravenous OA injection increased intra-tracheal pressure above vehicle injection. Intravenous NDGA administration (5mg/kg) reduced the intra-tracheal pressure increases. In a third series of experiments plasma leukotriene C₄ was measured by radio-immunoassay in 3 groups challenged with OA aerosol: vehicle-treated OA-sensitized, OA-sensitized receiving NDGA and vehicle treated guinea pigs. NDGA pretreatment reduced plasma LTC₄ in response to OA challenge in OA sensitized guinea pigs. This study demonstrates that NDGA is an effective antigenic agent when given by aerosol or intravenous injection in either conscious or anesthetized guinea pigs, respectively. The mechanism of action of NDGA is presumed primarily be due to the blockage of 5-lipoxygenase and therefore the synthesis of leukotrienes.

In Vivo Evaluation of 5-ASA Colon-Specific Tablets Using Experimental-Induced Colitis Rat Animal Model

Colonic drug delivery is intended not only for local treatment in inflammatory bowel disease (IBD) but also for systemic delivery of therapeutics. Intestinal myeloperoxidase (MPO) determination could be used to estimate the average level of inflammation in colon as well as to determine the efficacy of drugs to be used in the treatment of inflammatory bowel diseases or study the specificity of dosage forms to be used for colonic targeting of anti-inflammatory drugs. Colonic prodrug sulfasalazine (SASP) gets metabolized to give 5-aminosalicylic acid (5-ASA), which is the active portion of SASP. However, when given orally, 5-ASA is absorbed in upper part of gastrointestinal tract (GIT) and not made available in colon. In the present study, colon-targeted delivery of 5-ASA was achieved by formulating tablets with two natural polymers namely guar gum and pectin using compression coating method. Colonic specificity of 5-ASA tablets (prepared using guar gum and pectin as polymers) was evaluated in vitro using simulated fluids mimicking in vivo environment as well as in vivo method using chemically (2,4,6-trinitrobenzenesulfonic acid and acetic acid)-induced colitis rat model. Both colon-specific formulations of 5-ASA (guar gum and pectin) were observed to be more effective in reducing inflammation in chemically induced colitis rat models when compared to colon-specific prodrug sulfasalazine as well as conventional 5-ASA administered orally.

Plasma fatty acids as diagnostic markers in autistic patients from Saudi Arabia

Backgrounds

Autism is a family of developmental disorders of unknown origin. The disorder is characterized by behavioral, developmental, neuropathological and sensory abnormalities, and is usually diagnosed between the ages of 2 and 10 with peak prevalence rates observed in children aged 5-8 years. Recently, there has been heightened interest in the role of plasma free fatty acids (FA) in the pathology of neurological disorders. The aim of this study is to compare plasma fatty acid profiles of Saudi autistic patients with those of age-matching control subjects in an attempt to clarify the role of FA in the etiology of autism.

Methods

26 autistic patients together with 26-age-matching controls were enrolled in the present study. Methyl esters of FA were extracted with hexane, and the fatty acid composition of the extract was analyzed on a gas chromatography.

Results

The obtained data proved that fatty acids are altered in the plasma of autistic patients, specifically showing an increase in most of the saturated fatty acids except for propionic acid, and a decrease in most of polyunsaturated fatty acids. The altered fatty acid profile was discussed in relation to oxidative stress, mitochondrial dysfunction and the high lead (Pb) concentration previously reported in Saudi autistic patients. Statistical analysis of the obtained data shows that most of the measured fatty acids were significantly different in autistic patients compared to age -matching controls.

Conclusions

Receiver Operating Characteristic (ROC) curve analysis shows satisfactory values of area under the curve (AUC) which could reflect the high degree of specificity and sensitivity of the altered fatty acids as biomarkers in autistic patients from Saudi Arabia.

Role of bone marrow-derived monocytes/macrophages in the repair of mucosal damage caused by irradiation and/or anticancer drugs in colitis model

Mucosal damage is a common side effect of many cancer treatments, especially radiotherapy and intensive chemotherapy, which often induce bone marrow (BM) suppression. We observed that acetic acid- (AA-) induced mucosal damage in the colon of mice was worsened by simultaneous treatment with irradiation or 5-FU. However, irradiation 14 days prior to the AA treatment augmented the recovery from mucosal damage, suggesting that the recovery from BM suppression had an advantageous effect on the mucosal repair. In addition, BM transplantation also augmented the recovery from AA-induced mucosal damage. We further confirmed that transplanted BM-derived cells, particularly F4/80⁺Gr1⁺ “inflammatory” monocytes (Subset 1), accumulated in the damaged mucosal area in the early healing phase, and both of Subset 1 and F4/80⁺Gr1⁻ “resident” monocytes (Subset 2) accumulated in this area in later phases. Our results suggest that monocytes/macrophages contribute to the mucosal recovery and regeneration following mucosal damage by anticancer drug therapy.

Design, synthesis, and biological evaluation of (E)-3-(4-methanesulfonylphenyl)-2-(aryl)acrylic acids as dual inhibitors of cyclooxygenases and lipoxygenases

A group of (E)-3-(4-methanesulfonylphenyl)acrylic acids possessing a substituted-phenyl ring (4-H, 4-Br, 3-Br, 4-F, 4-OH, 4-OMe, 4-OAc, and 4-NHAc) attached to the acrylic acid C-2 position were prepared using a stereospecific Perkin condensation reaction. A related group of compounds having 4- and 3-(4-isopropyloxyphenyl)phenyl, 4- and 3-(2,4-difluorophenyl)phenyl and 4- and 3-(4-methanesulfonylphenyl)phenyl substituents attached to the acrylic acid C-2 position were also synthesized, using a palladium-catalyzed Suzuki cross-coupling reaction, for evaluation as dual cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) inhibitors. (E)-2-(3-Bromophenyl)-3-(4-methanesulfonylphenyl)acrylic acid (9h), and compounds having 4-(4-isopropyloxyphenyl-, 2,4-difluorophenyl-, or 4-methylsulfonylphenyl)phenyl moieties at the acrylic acid C-2 position (11a,b,d), were particularly potent COX-2 inhibitors with a high COX-2 selectivity index (COX-2 IC50 approximately 0.32 microM, SI > 316) similar to the reference drug rofecoxib (COX-2 IC50 = 0.5 microM, SI > 200). Acrylic acid analogs with a C-2 4-hydoxyphenyl (9d, IC50 = 0.56 microM), or 4-acetamidophenyl (9g, IC50 = 0.11 microM), substituent were particularly potent 5-LOX inhibitors that may participate in an additional specific hydrogen-bonding interaction. A number of compounds possessing a C-2 substituted-phenyl moiety (4-Br, 4-F, and 4-OH), or a 4- or 3-(2,4-difluorophenyl)phenyl moiety, showed potent 15-LOX inhibitory activity (IC50 values in the 0.31-0.49 microM range) relative to the reference drug luteolin (IC50 = 3.2 microM). Compounds having a C-2 4-acetylaminophenyl, or 4-(2,4-difluorophenyl)phenyl, moiety exhibited anti-inflammatory activities that were equipotent to aspirin, but less than that of celecoxib. The structure-activity data acquired indicate the acrylic acid moiety constitutes a suitable scaffold (template) to design novel acyclic dual inhibitors of the COX and LOX isozymes.

Polysaccharide peptides from COV-1 strain of Coriolus versicolor induce hyperalgesia via inflammatory mediator release in the mouse

Polysaccharide peptide (PSP), isolated from Coriolus versicolor COV-1, has been widely used as an adjunct to cancer chemotherapy and as an immuno-stimulator in China. In this study, the anti-nociceptive effects of PSP were investigated in two different pain models in the mouse. In the acetic acid-induced writhing model, initial studies showed that PSP decreased the number of acetic acid-induced writhing by 92.9%, which, by definition, would constitute an analgesic effect. However, further studies showed that PSP itself induced a dose-dependent writhing response. Studies on inflammatory mediator release showed that PSP increased the release of prostaglandin E2, tumor necrosis factor-alpha, interleukin-1beta, and histamine in mouse peritoneal macrophages and mast cells both in vitro and in vivo. The role of inflammatory mediator release in PSP-induced writhing was confirmed when diclofenac and dexamethasone decreased the number of writhing responses by 54% and 58.5%, respectively. Diphenhydramine totally inhibited the PSP-induced writhing. In the hot-plate test, PSP dose-dependently shortened the hind paw withdrawal latency, indicative of a hyperalgesic effect. The hyperalgesic effect was reduced by pretreatment with the anti-inflammatory drugs. In conclusion, the PSP-induced hyperalgesia was related to activation of peritoneal resident cells and an increase in the release of inflammatory mediators.

Synthesis and biological evaluation of 1,3-diphenylprop-2-yn-1-ones as dual inhibitors of cyclooxygenases and lipoxygenases

A new class of 1,3-diphenylprop-2-yn-1-ones possessing a p-MeSO2 COX-2 phamacophore on the C-3 phenyl ring was designed for evaluation as dual inhibitors of cyclooxygenase (COX) and lipoxygenase (LOX). Among the group of compounds evaluated, 1-(4-fluorophenyl)-3-(4-methanesulfonylphenyl)prop-2-yn-1-one (11j) exhibited excellent COX-2 inhibitory potency (COX-2 IC50 = 0.1 microM) and selectivity (SI = 300), whereas 1-(4-cyanophenyl)-3-(4-methanesulfonylphenyl)prop-2-yn-1-one (11d) exhibited an optimal combination of COX and LOX inhibition (COX-2 IC50 = 1.0 microM; COX-2 SI = 31.5; 5-LOX IC50 = 1.0 microM; 15-LOX IC50 = 3.2 microM).

Effect of nimesulide on acetic acid- and leukotriene-induced inflammatory bowel disease in rats

Inflammatory bowel disease (IBD) is a relapsing inflammation of intestine, which is mediated by release of inflammatory mediators. Both cyclo-oxygenase product prostaglandin (PGE2) and lipo-oxygenase product leukotriene (LTB4), may contribute to the pathogenesis of the inflammatory response. Nimesulide, a preferential COX-2 inhibitor was evaluated for its efficacy against experimental colitis in two different models (acetic acid- and LTB4-induced IBD) in rats. Inflammatory response was induced by intrarectal single administration of acetic acid or LTB4. Nimesulide (9 and 18 mg/kg, p.o.) significantly prevented development of inflammatory changes, decreased myeloperoxidase (MPO) activity, and also restored the altered contractility response of the isolated colon segment to KCl. The results suggested the involvement of both cyclo-oxygenase (COX) and lipo-oxygenase-mediated proinflammatory agents in colonic inflammatory process associated with IBD. Further, this study suggests that such therapeutic interventions may be of value in the treatment of IBD.

Recent advances in the treatment of psoriatic arthritis

This article provides an overview of recent developments in the treatment of psoriatic arthritis with an emphasis on patent literature for the period January 1998 to December 2002. The main pathogenic pathways thought to be operative in psoriatic arthritis are highlighted and some novel compounds that can potentially interfere with such pathways at different levels are discussed. Among the new agents proposed, the inhibitors of cytokine signaling, angiogenesis, and extracellular matrix degradation appear to be of particular interest for the treatment of psoriatic arthritis resistant to conventional therapies. Finally, new formulations of existing drugs and natural remedies claimed to be useful for the treatment of psoriatic arthritis are reviewed.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Participation of corticosteroids and effects of indomethacin on the acute inflammatory response of rats fed n-6 or n-3 polyunsaturated fatty acid-rich diets

We have previously shown that both n-3 (fish oil) and n-6 (soybean oil) PUFA-rich diets reduce carrageenan-induced paw edema in rats. The present study evaluated the role of corticosteroids, and the effect of indomethacin on this response. Basal (pre-carrageenan) levels of corticosterone were elevated in both lipid diets compared to the chow diet. During inflammation, corticosterone levels increased to a similar extent in the chow and lipid diets. With 2.0 mg/kg indomethacin, edema was reduced in the chow diet and the n-3 diet, while it was not changed in the n-6 diet. In contrast, the 16.6 mg/kg dose of indomethacin induced a mild increase in edema in the chow diet but a pronounced edema increase in the lipid diets. The increase in corticosterone levels induced by carrageenan was either reduced (chow) or completely abolished (lipids) by the treatment with the higher dose of indomethacin, compared to both the control (untreated) group, and the lower dose of indomethacin. These data indicate that both acute inflammation and the response to an antiinflammatory drug were attenuated by n-3 or n-6 PUFA-rich diets. They also showed that indomethacin can have anti- or proinflammatory properties reflecting the extent of the corticosterone inhibition by indomethacin.

Effect of E3040, an inhibitor of 5-lipoxygenase and thromboxane synthase, on rat bowel damage induced by lipopolysaccharide

Intravenous administration of lipopolysaccharide to rats that had been immunized with lipopolysaccharide induced hemorrhagic damage in the large intestine. We investigated the role of 5-lipoxygenase and thromboxane synthase products in the damage of the large intestine induced by lipopolysaccharide. In the large intestine of lipopolysaccharide-immunized rats, intravenous injection of lipopolysaccharide increased the vascular permeability, production of leukotriene B(4), leukotriene C(4)/D(4), thromboxane B(2) and prostaglandin E(2), and also increased the activity of myeloperoxidase, a marker enzyme of neutrophils. Oral administration of E3040 (6-hydroxy-5,7-dimethyl-2-(methylamino)-4-(3-pyridylmethyl)benzothiazole), a novel dual inhibitor of 5-lipoxygenase and thromboxane synthase, at 30 and 100 mg/kg inhibited the increase in vascular permeability induced by lipopolysaccharide in the large intestine. E3040 inhibited the production of leukotriene B(4) and thromboxane B(2) and tended to increase the production of prostaglandin E(2) in the large intestine. Sulfasalazine (500 mg/kg) and prednisolone (10 mg/kg), drugs used for the treatment of inflammatory bowel disease, had no significant effect on eicosanoid production and vascular permeability. These results indicate that E3040 inhibits the production of both leukotriene B(4) and thromboxane B(2) and prevents lipopolysaccharide-induced damage in the large intestine of lipopolysaccharide-immunized rats.

Secretory event in intestinal grafts during preservation ischemia

BACKGROUND

Ischemia triggers secretion of proteins from the intestine, including type II secretory phospholipase A2 (sPLA2). This "secretory event" was studied in intestinal grafts during the first few hours of preservation by measuring total protein, sPLA2, and other enzymes in the UW preservation solution over time. The effect of PX-13, a PLA2 inhibitor, was also studied.

MATERIALS AND METHODS

Twenty-five centimeter intestinal grafts were harvested from Lewis rats, flushed, and preserved in UW solution +/- PX-13 at 4 degrees C. UW samples from 0 to 48 h (n = 5 each) were analyzed for total protein, sPLA2, lactate dehydrogenase (LDH), N-acetylglucosamine (NAGA), and lysozyme. Nonpreserved grafts were homogenized in PBS as tissue controls. Standard biochemical methods were used for all assays.

RESULTS

Total protein increased rapidly by 5 min, continued to rise more slowly until 30 min, and then stabilized. The most significant increase in sPLA2 activity occurred between 90 and 180 min. NAGA increased most markedly between 30 and 180 min, while LDH increased in the first 30 min, although the level of both enzymes was negligible compared to tissue enzyme. Lysozyme levels were minimal at all times. PX-13 decreased sPLA2 activity markedly at all time points.

CONCLUSION

Total protein levels increased before sPLA2, suggesting that sPLA2 may be secreted in response to other proteins or enzymes released even earlier during preservation (e.g., cytokines). These elevations do not appear to be caused by cell death. Phospholipase A2 secretion may be blocked, and this may greatly improve the outcome of intestinal preservation.

Inhibitory effect of nordihydroguaiaretic acid on the frequency of micronuclei induced by methyl methanesulfonate in vivo

Nordihydroguaiaretic acid (NDGA) is an antioxidant originally obtained from plants of the genus Larrea. This chemical has shown antigenotoxic activity measuring gene mutations and sister-chromatid exchanges. The aim of this investigation was to determine if NDGA is also an antigenotoxic agent and can inhibit the induction of micronucleus (MN) formation by methyl methanesulfonate (MMS) in mouse. The frequency of micronucleated polychromatic erythrocytes (MPE) was scored for 4 days, and a MN induction curve by a single injection of MMS (40 mg/kg) was obtained. The results of this experiment showed that the highest MN incidence was reached at the second day of exposure with a mean of 13.2%+/-1.0. This value is more than 4 times the control mean. Thus, the modulatory study by NDGA was established at a 2-day exposure time using three doses (6.0, 11.0, and 17.0 mg/kg) against the damage induced by 40 mg/kg of MMS. The results of this study showed a significant reduction of the clastogenic damage at the two highest doses, where the inhibitory values corresponded to 62.2% and 66.7%, respectively. With respect to the ratio polychromatic erythrocytes/normochromatic erythrocytes, a marked toxicity was detected with 2 days of MMS exposure; however, the combination of the two high doses of NDGA plus MMS significantly reduced the cytotoxic damage produced by MMS alone.

In vivo and in vitro antigenotoxic effect of nordihydroguaiaretic acid against SCEs induced by methyl methanesulfonate

Nordihydroguaiaretic acid (NDGA) is a phenolic lignan which has shown to cause a variety of actions potentially useful for human health; therefore, in this investigation we determined its capacity for inhibiting the rate of sister chromatid exchanges (SCEs) induced by methyl methanesulfonate (MMS). We tested the effect of 0.25, 0.50, 1.0, and 2.0 microM of NDGA on the damage exerted by 55 microM of MMS. Cultured human lymphocytes from two female donors were used for the experiment. The best result concerning its modulatory action was obtained with 1.0 microM of NDGA; with this dose the mean inhibitory index including both donors reached 68.2%. The values obtained for the mitotic and proliferative indexes were not significantly modified with respect to the basal data. We also used the mouse bone marrow in vivo system to evaluate the inhibitory effect of the chemical. In this study we tested 1.0, 6.0, and 11.0 mg/kg of NDGA intraperitoneally (i.p.) administered 1 h before an i.p. injection of MMS (40 mg/kg). The best inhibitory index in this model corresponded to the dose of 11 mg/kg of NDGA (86.9%). The mitotic index and the average generation time showed no significant variation with respect to the control data. Our study established that NDGA produces antigenotoxic action in mammalian cells in vitro and in vivo.

Antiinflammatory effects of human milk on chemically induced colitis in rats

We examined the effects of a human milk diet on rats with chemical colitis induced with a 4% acetic acid enema. Colonic myeloperoxidase activity was used as a surrogate marker for neutrophil infiltration. Control rats fed rat chow had little colonic myeloperoxidase activity; geometric mean, 0.27 U/g of tissue. Rats with colitis fed rat chow had significantly increased colonic myeloperoxidase activity (geometric mean, 6.76 U/g, p < 0.01 versus no colitis), as did rats with colitis fed infant formula or Pedialyte (geometric mean, 6.92 and 8.13 U/g, respectively, both p < 0.01 versus no colitis). Animals with colitis fed human milk had significantly lower colonic myeloperoxidase activity (geometric mean, 2.34 U/g) than did animals with colitis fed either chow or infant formula (p < 0.001). Similar effects were seen in rats with colitis fed infant formula supplemented with recombinant human IL-1 receptor antagonist (geometric mean, 1.95 U/g). These data show that orally administered human milk has an antiinflammatory effect on chemically induced colitis in rats, which may be mediated in part by IL-1 receptor antagonist contained in human milk.

Pharmacological activity of the second generation leukotriene B4 receptor antagonist, SC-53228: effects on acute colonic inflammation and hepatic function in rodents

Inflammatory bowel disease is a chronic inflammatory disorder of the gastrointestinal tract that includes ulcerative colitis and Crohn's disease. Leukotriene B4 is thought to be a prominent proinflammatory mediator in these diseases, in that leukotriene B4 levels are increased in the colonic mucosa of inflammatory bowel disease patients and there is increased polymorphonuclear leukocyte infiltration of these tissues. SC-53228 [(+)-(S)-7-[3-[2(-cyclopropylmethyl)-3-methoxy-4- [(methylamino)carbonyl]phenoxy]propoxy]-3,4-dihydro-8-propyl-2H-1- benzopyran-2-propanoic acid], a second generation LTB4 receptor antagonist, was evaluated for therapeutic efficacy in a rodent model of acute colonic inflammation induced by short chain organic acids, as well as for effects on rodent liver. When given intracolonically to mice, SC-53228 inhibited neutrophil infiltration, assessed by myeloperoxidase (MPO) levels, with an ED50 value of 9 +/- 1.2 mg/kg. When given by gavage, SC-53228 inhibited neutrophil influx in colitic mice with an ED50 value of 30 mg/kg. These results were also confirmed histologically. Furthermore, high dose oral SC-53228 treatment had no effect on liver cytochrome P-450 content, fatty acyl CoA oxidase or liver weight in rats and mice. Together, these data suggest that SC-53228 may be efficacious orally and locally, as well as safe for use in trials for the medical management of IBD.

Colonic delivery of dexamethasone from a prodrug accelerates healing of colitis in rats without adrenal suppression

BACKGROUND/AIMS

Dexamethasone-beta-D-glucuronide, a colon-specific prodrug of dexamethasone, may be useful in the treatment of ulcerative colitis and Crohn's colitis. The aim of this study was to evaluate colonic delivery and efficacy of this prodrug in the rat.

METHODS

Distribution of dexamethasone in luminal contents and tissues of the gastrointestinal tract and in plasma was measured after oral administration of dexamethasone-beta-D-glucuronide or free dexamethasone. Efficacy of the prodrug and free drug was tested in an acetic acid-induced rat colitis model. Healing of induced colitis was assessed by measuring net intestinal fluid absorption, colonic surface area of ulceration, histology, and myeloperoxidase activity. Glucocorticosteroid toxicity was evaluated with serum corticosterone and plasma adrenocorticotropic hormone levels.

RESULTS

The drug delivery index (a measure of relative targeting efficiency) was 6.7 and 8.6 in the cecal and colonic mucosa, respectively. The prodrug was significantly more potent than free drug in improving net colonic fluid absorption while significantly reducing surface area of ulceration and histological grade in colitic rats. Treatment with free dexamethasone significantly reduced serum corticosterone levels to subnormal levels, and treatment with the prodrug maintained serum corticosterone and plasma adrenocorticotropic hormone levels near control levels.

CONCLUSIONS

The prodrug dexamethasone-beta-D-glucuronide delivers efficacious amounts of dexamethasone to the large intestine from lower doses than free dexamethasone.

Induction of neutrophil Mac-1 integrin expression and superoxide production by the medicinal plant extract gossypol

Gossypol is present in antiinflammatory poultices made from the medicinal tree Thespesia populnea. Isolated human neutrophils exposed to 3-20 microM gossypol for 15-90 min were assayed in vitro for superoxide production and surface expression of Mac-1 (CD11b/CD18). Gossypol increased superoxide production in a time- and concentration-dependent fashion consistent with a moderate, delayed respiratory burst. Surface Mac-1 expression was increased within 15 min by 3-5 microM gossypol, resulting in a 14-fold increase over controls and a threefold greater increase over that produced by PMA. Staurosporine failed to block gossypol induction of superoxide and Mac-1, while EDTA inhibited induction of Mac-1 only, implicating a calcium-dependent mechanism. Gossypol increased intracellular calcium to peak levels, but in a delayed fashion as compared to FMLP. These findings demonstrate that gossypol is a highly potent stimulant of Mac-1 expression and suggest at least two protein kinase C-independent pathways of neutrophil activation. The resultant exhaustion of neutrophils may account for the antiinflammatory properties of plants containing gossypol.

Topical anticolitic efficacy and selectivity of the glucocorticoid budesonide in a new model of acetic acid-induced acute colitis in the rat

AIMS

To study the effect of local or parenteral administration of the glucocorticoid budesonide in the acetic acid-induced colitis model in the rat.

METHODS

Colitis was induced in an exteriorized colonic segment by administration of 4% acetic acid for 15 s. Four days later, this colonic segment with colitis was examined using a morphological scoring system, and measurements of myeloperoxidase activity and of plasma exudation into the colonic segment. The experimental colitis showed morphological similarities to human ulcerative colitis, with 3-fold increase in myeloperoxidase activity and 6-fold increase in the plasma exudation. Budesonide in different doses administered for 3 days, starting one day after acetic acid instillation, prevented the development of colitis in a dose-dependent manner. The best effect of budesonide on the morphological score was achieved after local treatment at a dose of 10(-5) M twice daily (76% reduction compared with a control colitis group) and parenteral treatment with 0.75 mg/kg (80% reduction). These doses also normalized myeloperoxidase activity and significantly reduced the plasma exudation. The systemic effects of the drug were most pronounced in the group treated with parenteral budesonide. This group showed the greatest reduction in body weight and a significant reduction of the weight of adrenal glands and spleen (as compared to controls). Thymus weight in animals treated systemically was significantly lower than in locally treated animals. In the group treated with local budesonide the weight of adrenals was reduced. However, the weights of spleen and thymus were not reduced and the reduction of the body weight was even less than in the control group.

CONCLUSION

Local treatment with budesonide at a dose of 10(-5) M (0.17 mg/kg if completely absorbed, but only 0.03 mg/kg with 15% bioavailability on colonic application) was as effective as parenteral treatment at a dose of 0.75 mg/kg in the attenuation of acetic acid-induced colitis in the rat, but resulted in minor systemic side-effects.

Effect of putative phospholipase A2 inhibitors on acetic acid-induced acute colitis in the rat

Phospholipase activation may play an important role in ulcerative colitis. This hypothesis was tested by evaluating the effect of two non-selective phospholipase (PL) A2 inhibitors, quinacrine and p-bromophenacyl-bromide (pBPB), on acetic acid-induced colitis in the rat. The calcium antagonist verapamil, which may also act as a PLA2 inhibitor, was also tested. Acute colitis was induced in an isolated colonic segment by instillation of 4 per cent acetic acid for 15 s; this induces a uniform colitis after 4 days. The severity of colitis was evaluated histologically, by measuring myeloperoxidase (MPO) activity and by determining plasma exudation into the lumen of the colon (permeability) with 125I-labelled albumin given intravenously. All three putative PLA2 inhibitors tested were found to prevent the development of colitis. Intravenous administration of quinacrine 10 mg kg-1 at 30 min before instillation of acetic acid resulted in a normal mucosal appearance, normal MPO activity and a significantly reduced increase in plasma exudation into the colon. A similar effect was achieved using verapamil. Intracolonic administration of either quinacrine or pBPB also prevented acetic acid-induced colitis. However, three doses, starting immediately after acetic acid administration and repeated on the first and second days, were needed to achieve this, whereas one dose produced only a partial effect. PLA2 may play an important role in acetic acid-induced colitis and inhibition of its activity may offer an alternative mode of treatment in ulcerative colitis.

Effects of zileuton, a new 5-lipoxygenase inhibitor, in experimentally induced colitis in rats

The efficacy of zileuton, a new 5-lipoxygenase inhibitor, was investigated in comparison with sulphasalazine in an experimental model of rat colitis. Under light anaesthesia with ether, male rats were subjected to intracolonic administration of trinitrobenzene sulfonic acid (TNB) in 50% ethanol and were then sacrificed 2, 4 and 7 days after colitis induction. Untreated rats exhibited elevated colonic levels of leukotriene B4 (LTB4) and 6-keto-PGF1 alpha, and an increase in colonic myeloperoxidase (MPO) activity (investigated as an index of leukocyte adhesion and accumulation). Moreover, ulceration and inflammation of the distal colon with formation of granuloma and pathologic connections were observed. Treated rats received zileuton or sulphasalazine (50 mg/kg per os twice a day) 24 h before the induction of colitis until they were sacrificed. Treatment with the specific 5-lipoxygenase inhibitor, zileuton, resulted in significant reductions of colonic leukotriene B4 and 6-keto-PGF1 alpha synthesis, macroscopic and histological colonic damage and colonic inflammation as assessed by the measurement of MPO activity. In contrast, sulphasalazine had a lower effect than zileuton on LTB4 and MPO levels (p < 0.05), while it was able to reduce colonic damage and 6-keto-PGF1 alpha levels as well as zileuton. This study shows, therefore, that zileuton is effective in attenuating the lesions in an experimental model of colitis. Furthermore, the results are consistent with the hypothesis that leukotrienes play an important role in the pathogenesis of intestinal bowel diseases (IBD).

NPC 15669, an inhibitor of neutrophil recruitment, is efficacious in acetic acid-induced colitis in rats

BACKGROUND

The efficacy of the leukocyte recruitment inhibitor, N-[9H-2,7-dimethylfluoren-9-ylmethoxy)carbonyl]-L-leucine (NPC 15669) was compared with drugs used to treat inflammatory bowel diseases in a rat model, acetic acid-induced colitis.

METHODS

Colonic damage assessed by visual inspection, histological quantitation of tissue injury, vascular permeability, myeloperoxidase (MPO) accumulation, and synthesis of inflammatory mediators were measured.

RESULTS

Intrarectal pretreatment with NPC 15669 results in a significant reduction of all measured indices of inflammation. The median effective dose (ED50) of NPC 15669 for inhibition of MPO accumulation and vascular permeability is 13.2 mg/kg and 31 mg/kg, respectively. The active moiety of sulfasalazine, 5-aminosalicylic acid (5-ASA), the antioxidant/5-lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA) and the corticosteroids dexamethasone and hydrocortisone, yielded ED50 values (MPO accumulation) of 68 mg/kg, 95 mg/kg, 0.7 mg/kg, and 13 mg/kg, respectively. When formulated suspensions of NPC 15669, 5-ASA, or dexamethasone were used, potency was increased 10-40-fold. Furthermore, NPC 15669 (10 mg/kg) administered 7 hours after acetic acid and evaluated 24 hours after acetic acid administration significantly attenuated neutrophil influx (70% inhibition of MPO accumulation), whereas 5-ASA (100 mg/kg) displayed no therapeutic effects.

CONCLUSIONS

NPC 15669 may be useful in the treatment of inflammatory disorders.

Free radicals and other reactive oxygen metabolites in inflammatory bowel disease: cause, consequence or epiphenomenon?

Oxygen-derived free radicals and other reactive oxygen metabolites have emerged as a common pathway of tissue injury in a wide variety of otherwise disparate disease processes. This has given rise to the hope that efforts directed towards the pharmacologic control of free radical-mediated tissue injury (Reilly, P.M., Schiller, H. J. and Bulkley, G. B. (1991) Pharmacologic approach to tissue injury mediated by free radicals and other reactive oxygen metabolites. Am. J. Surg. 161: 488-503) may have particular application to patients suffering from Crohn's disease and/or ulcerative colitis. However, because tissue injury by any mechanism, even direct mechanical trauma, can elicit an inflammatory response which entails the secondary generation of toxic oxidants by neutrophils and tissue macrophages, it is important that the evidence for this association be examined critically, so as to discriminate the possibility of an etiologic role for these toxic compounds from their presence as a reflection of injury caused primarily by other agents. Similarly, in considering the therapeutic potential of free radical ablation for the treatment of patients with IBD it is important to distinguish between interventions that might specifically block the fundamental injury mechanism from those which would act in a more nonspecific, anti-inflammatory role.

Role of neutrophils in acetic acid-induced colitis in rats

Intrarectal administration of 4% acetic acid produces diffuse inflammation that ultimately results in erosions and ulcerations of the rat colon. Although this model of colitis has been used extensively over the past several years, there are no quantitative data available regarding the relationship between neutrophil infiltration and mucosal injury during times of active inflammation. Therefore, the objective of this study was to define the role of extravasated neutrophils as mediators of mucosal injury and inflammation in acetic acid-induced colitis. We found the intrarectal administration of 4% acetic acid produced an 11-fold increase in colonic mucosal permeability, a 9-fold increase in colonic MPO activity, and a 1.6-fold increase in colon weight at 48 h following administration of acetic acid. In addition, we found significant correlations between colonic MPO activity and mucosal permeability and between colonic MPO activity and colon weight (P less than 0.01 for both). These data suggested that inflammatory neutrophils may mediate mucosal injury and inflammation in this model of colitis. To assess the role of circulating neutrophils, rats were rendered neutropenic for 48 h by the intraperitoneal administration of antiserum directed toward rat neutrophils (ANS). Although ANS treatment reduced both the number of circulating neutrophils and colonic MPO activity to less than 10% of control values, it did not attenuate the increases in colonic mucosal permeability nor did it attenuate the increases in colon weight produced by acetic acid. Histological inspection confirmed that ANS treatment was not effective in attenuating the injury to the epithelial barrier. These data demonstrate that infiltrating neutrophils do not mediate the mucosal injury and inflammation observed in acetic acid-induced colitis.

Reactive oxygen metabolites and colitis: a disturbed balance between damage and protection. A selective review

Enhanced local production of reactive oxygen metabolites has been found in association with colitis, both experimentally and in humans. Cellular and biochemical systems involved have been identified, and 5-aminosalicylic acid-containing drugs but, more effectively, specific scavengers have been found to reduce the intestinal inflammatory process. The multitude of reactions in which oxygen metabolites participate provides a new area of research in intestinal inflammation. These basic studies might bring related clinical studies in an era of new anti-inflammatory drugs for inflammatory bowel disease specifically designed to scavenge toxic oxygen metabolites.