Screening a small molecule library to identify inhibitors of NF-κB inducing kinase and pro-labor genes in human placenta

The non-canonical NF-κB signaling (RelB/p52) pathway drives pro-labor genes in the human placenta, including corticotropin-releasing hormone (CRH) and cyclooxygenase-2 (COX-2), making this a potential therapeutic target to delay onset of labor. Here we sought to identify small molecule compounds from a pre-existing chemical library of orally active drugs that can inhibit this NF-κB signaling, and in turn, human placental CRH and COX-2 production. We used a cell-based assay coupled with a dual-luciferase reporter system to perform an in vitro screening of a small molecule library of 1,120 compounds for inhibition of the non-canonical NF-κB pathway. Cell toxicity studies and drug efflux transport MRP1 assays were used to further characterize the lead compounds. We have found that 14 drugs have selective inhibitory activity against lymphotoxin beta complex-induced activation of RelB/p52 in HEK293T cells, several of which also inhibited expression of CRH and COX-2 in human term trophoblast. We identified sulfapyridine and propranolol with activity against CRH and COX-2 that deserve further study. These drugs could serve as the basis for development of orally active drugs to affect length of gestation, first in an animal model, and then in clinical trials to prevent preterm birth during human pregnancy.

The effect of sulfasalazine and its active components on human polymorphonuclear leukocyte function in relation to ulcerative colitis

Sulfasalazine and its active components, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), are potent modulators of inflammatory reactions but with somewhat different modes of action. Investigating the effect of these compounds on normal human polymorphonuclear leukocytes in vitro, we show inhibition of different stages in the phagocytic process, such as migration (sulfasalazine and SP), superoxide production (sulfasalazine and SP), myeloperoxidase-mediated iodination and cytotoxicity (5-ASA and SP). It is thus suggested that sulfasalazine is not just a vehicle for delivering its active components in the colon, but that its therapeutic effect is ulcerative colitis and other inflammatory reactions is a result of the concurrent action of the three compounds.

On the action of 5-amino-salicylic acid and sulfapyridine on M. avium including subspecies paratuberculosis

Background

Introduced in 1942, sulfasalazine (a conjugate of 5-aminosalicylic acid (5-ASA) and sulfapyridine) is the most prescribed medication used to treat “inflammatory” bowel disease (IBD.) Although controversial, there are increasingly compelling data that Mycobacterium avium subspecies paratuberculosis (MAP) may be an etiological agent in some or all of IBD. We have shown that two other agents used in the therapy of IBD (methotrexate and 6-MP) profoundly inhibit MAP growth. We concluded that their most plausible mechanism of action is as antiMAP antibiotics. We herein hypothesize that the mechanism of action of 5-ASA and/or sulfapyridine may also simply be to inhibit MAP growth.

Methodology

The effect on MAP growth kinetics by sulfasalazine and its components were evaluated in bacterial culture of two strains each of MAP and M. avium, using a radiometric (¹⁴CO₂ BACTEC®) detection system that quantifies mycobacterial growth as arbitrary “growth index units” (GI). Efficacy data are presented as “percent decrease in cumulative GI” (%−ΔcGI).

Principal Findings

There are disparate responses to 5-ASA and sulfapyridine in the two subspecies. Against MAP, 5-ASA is inhibitory in a dose-dependent manner (MAP ATCC 19698 46%−ΔcGI at 64 µg/ml), whereas sulfapyridine has virtually no effect. In contrast, against M. avium ATCC 25291, 5-ASA has no effect, whereas sulfapyridine (88%−ΔcGI at 4 µg/ml) is as effective as methotrexate, our positive control (88%−ΔcGI at 4 µg/ml).

Conclusions

5-ASA inhibits MAP growth in culture. We posit that, unknowingly, the medical profession has been treating MAP infections since sulfasalazine's introduction in 1942. These observations may explain, in part, why MAP has not previously been identified as a human pathogen. We conclude that henceforth in clinical trials evaluating antiMAP agents in IBD, if considered ethical, the use of 5-ASA (as well as methotrexate and 6-MP) should be excluded from control groups.

Sulfasalazine reduces bile acid induced apoptosis in human hepatoma cells and perfused rat livers

BACKGROUND

Bile acid induced apoptosis in hepatocytes can be antagonised by nuclear factor kappaB (NFkappaB) dependent survival pathways. Sulfasalazine modulates NFkappaB in different cell types. We aimed to determine the effects of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid (5-ASA) on bile acid induced apoptosis in hepatocytes.

METHODS

Apoptosis was determined by caspase assays and immunoblotting, NFkappaB activation by electrophoretic mobility shift assay and reporter gene assays, generation of reactive oxygen species (ROS) fluorometrically, bile secretion gravimetrically, and bile acid uptake radiochemically and by gas chromatography in HepG2-Ntcp cells and isolated perfused rat livers.

RESULTS

Glycochenodeoxycholic acid (GCDCA 75 micromol/l) induced apoptosis was reduced by sulfasalazine dose dependently (1-1000 micromol/l) in HepG2-Ntcp cells whereas its metabolites 5-ASA and sulfapyridine had no effect. Sulfasalazine significantly reduced GCDCA induced activation of caspases 9 and 3. In addition, sulfasalazine activated NFkappaB and decreased GCDCA induced generation of ROS. Bile acid uptake was competitively inhibited by sulfasalazine. In perfused rat livers, GCDCA (25 micromol/l) induced liver injury and extensive hepatocyte apoptosis were significantly reduced by simultaneous administration of 100 micromol/l sulfasalazine: lactate dehydrogenase and glutamate-pyruvate transaminase activities were reduced by 82% and 87%, respectively, and apoptotic hepatocytes were observed only occasionally. GCDCA uptake was reduced by 45 (5)% when sulfasalazine was coadministered. However, when 50% of GCDCA (12.5 micromol/l) was administered alone, marked hepatocyte apoptosis and liver injury were again observed, questioning the impact of reduced GCDCA uptake for the antiapoptotic effect of sulfasalazine.

CONCLUSION

Sulfasalazine is a potent inhibitor of GCDCA induced hepatocyte apoptosis in vitro and in the intact liver.

Free radical scavenging reactions of sulfasalazine, 5-aminosalicylic acid and sulfapyridine: mechanistic aspects and antioxidant activity

Reactions of sulfasalazine (SAZ) and its metabolites, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), with various oxidizing and reducing free radicals (hydroxyl, haloperoxyl, one-electron oxidizing, lipid peroxyl, glutathiyl, superoxide, tryptophanyl, etc.) have been studied to understand the mechanistic aspects of its action against free radicals produced during inflammation. Nanosecond pulse radiolysis technique coupled with transient spectrophotometry has been used for in situ generation of free radicals and to follow their reaction pathways. The transients produced in these reactions have been assigned and radical scavenging rate constants have been measured. In addition to scavenging of various primary and secondary free radicals by SAZ, 5-ASA and SP, 5-ASA has also been observed to efficiently scavenge radicals of biomolecules. 5-ASA has been found to be the active moiety of SAZ involved in the scavenging of oxidizing free radicals whereas reduction of SAZ produced molecular radical anion. The study suggests that free radical scavenging activity of 5-ASA may be a major path of pharmacological action of SAZ against inflammatory bowel diseases (IBD).

Induction of T lymphocyte apoptosis by sulphasalazine in patients with Crohn's disease

BACKGROUND

Lamina propria T lymphocytes (LPL) of the intestinal mucosa are chronically activated in Crohn's disease (CD). Defective apoptosis of activated LPL was proposed as a key pathogenic mechanism. In fact, increased expression of antiapoptotic molecules was observed in CD LPL. In the present work, we aimed to analyse the effects and underlying molecular mechanisms of 5-amino salicylic acid (5-ASA) and derivatives on apoptosis of LPL and peripheral blood lymphocytes (PBL) in patients with CD compared with ulcerative colitis (UC) and in non-inflammatory controls.

METHODS

PBL and LPL were isolated by Ficoll-Hypopaque gradient centrifugation and the EGTA-collagenase method, respectively. PBL/LPL were stimulated with FasL, 5-ASA, sulphapyridine, and sulphasalazine for 24/48 hours and apoptosis was quantified by flow cytometry (annexin V- propidium iodide method) and immunofluorescence. The molecular mechanisms of drug induced apoptosis were analysed in wild-type and FADD-/- Jurkat T cells using western blots and caspase assays.

RESULTS

While PBL displayed a normal apoptosis pattern after Fas stimulation in patients with active CD, LPL from inflammatory areas were highly resistant. Comparable resistance to apoptosis was observed in LPL of UC patients. In contrast with 5-ASA, which did not induce apoptosis in lymphocytes, sulphasalazine proved to be a potent proapoptotic agent. Sulphasalazine induced T lymphocyte apoptosis was independent of the Fas pathway but associated with marked downregulation of antiapoptotic bcl-xl and bcl2, activation of the mitochondrial apoptosis signalling pathway, and subsequent activation of caspase-9 and caspase-3.

CONCLUSION

The beneficial effect of sulphasalazine in treating inflammatory bowel disease is at least in part attributable to its proapoptotic effects on LPL which allows potent downregulation of lymphocyte activation.

Susceptibility of Desulfovibrio desulfuricans intestinal strains to sulfasalazine and its biotransformation products

BACKGROUND

Desulfovibrio desulfuricans intestinal bacteria may contribute to toxic hydrogen sulfide production in the human gut. Our objective was to examine whether the D. desulfuricans strains isolated from the human body are susceptible to sulfasalazine (SAS) and the products of its biotransformation, i.e. 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), in order to determine the relationship between the strains' susceptibility to SAS and their ability to reduce the azo bond within this drug.

MATERIAL/METHODS

Six wild strains of D. desulfuricans (isolated from feces and biopsy specimens from patients with colitis ulcerosa, Crohn's disease, irritable bowel syndrome, colonic diverticula, primary biliary cirrhosis, or tubular adenomas of the colon) were cultured in the presence of SAS, 5-ASA, and SP. Growth inhibition coefficients were compared with coefficients of inhibition of the azo-bond reduction in SAS.

RESULTS

The D. desulfuricans strains present in the human digestive tract were susceptible to a small degree to SAS and to 5-ASA and SP.

CONCLUSIONS

The intestinal D. desulfuricans strains differed in their susceptibility to SAS and its biotransformation products. The strains showing higher susceptibility to SAS lost the ability to reduce the azo bond in this drug, which may be attributed to the lower metabolic activity of the bacteria. The presence of D. desulfuricans in the large intestines of patients with ulcerative colitis and the confirmed diversity of the biological activity of the isolated strains demonstrate the need for clinical examination of the role of these bacteria in the development of some inflammatory disorders.

The effect of sulfasalazine on rheumatoid arthritic synovial tissue chemokine production

Rheumatoid arthritis (RA) is an aggressive inflammatory disease in which chemokines are thought to recruit leukocytes and induce angiogenesis. The aim of this study was to investigate the effects of sulfasalazine (SASP) and its metabolites, sulfapyridine (SP), and 5-aminosalicylic acid (5ASA) on chemokine production by RA synovial tissue explants and interleukin (IL)-1beta-stimulated RA synovial tissue fibroblasts using enzyme-linked immunosorbent assays and flow cytometry. Synovial tissue explants from RA patients secreted a decreased amount of the chemokines IL-8 and growth-related gene product alpha (GROalpha) when treated with SASP over a broad range of concentrations based on the typical clinical dosage of 2 g/day. SP had a significant effect in that it decreased RA synovial tissue explant secretion of IL-8 (22%), GROalpha (55%), and monocyte chemotactic protein-1 (MCP-1) (42%) (P < 0.05). 5ASA had no effect on RA synovial tissue explant production of IL-8 and MCP-1, while increasing GROalpha production. In IL-1beta-stimulated RA synovial tissue fibroblasts, SASP significantly increased chemokine secretion, while SP significantly decreased IL-8 (24%) and GROalpha (21%) secretion (P < 0.05). Flow cytometry showed that the number of IL-8 expressing RA synovial tissue fibroblasts did not significantly change following SP treatment. These data suggest that SASP may function to reduce inflammation in RA through the effects of its metabolite SP to reduce the secretion of the inflammatory chemokines IL-8, GROalpha, and MCP-1.

Sulphasalazine inhibits macrophage activation: inhibitory effects on inducible nitric oxide synthase expression, interleukin-12 production and major histocompatibility complex II expression

The anti-inflammatory agent sulphasalazine is an important component of several treatment regimens in the therapy of ulcerative colitis, Crohn's disease and rheumatoid arthritis. Sulphasalazine has many immunomodulatory actions, including modulation of the function of a variety of cell types, such as lymphocytes, natural killer cells, epithelial cells and mast cells. However, the effect of this agent on macrophage (M phi) function has not been characterized in detail. In the present study, we investigated the effect of sulphasalazine and two related compounds - sulphapyridine and 5-aminosalicylic acid - on M phi activation induced by bacterial lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). In J774 M phi stimulated with LPS (10 microg/ml) and IFN-gamma (100 U/ml), sulphasalazine (50-500 microM) suppressed nitric oxide (NO) production in a concentration-dependent manner. The expression of the inducible NO synthase (iNOS) was suppressed by sulphasalazine at 500 microM. Sulphasalazine inhibited the LPS/IFN-gamma-induced production of both interleukin-12 (IL-12) p40 and p70. The suppression of both NO and IL-12 production by sulphasalazine was superior to that by either sulphapyridine or 5-aminosalicylic acid. Although the combination of LPS and IFN-gamma induced a rapid expression of the active forms of p38 and p42/44 mitogen-activated protein kinases and c-Jun terminal kinase, sulphasalazine failed to interfere with the activation of any of these kinases. Finally, sulphasalazine suppressed the IFN-gamma-induced expression of major histocompatibility complex class II. These results demonstrate that the M phi is an important target of the immunosuppressive effect of sulphasalazine.

Inhibitory effect of mast cell-mediated immediate-type allergic reactions by sulfapyridine

We examined the effect of sulfapyridine on mast cell-mediated immediate-type allergic reactions. Sulfapyridine (1 and 10 microg/kg) significantly inhibited systemic allergic reaction induced by compound 48/80 in rats. Sulfapyridine (1 and 10 microg/kg) also inhibited significantly local mast cell-mediated immediate-type allergic reactions activated by anti-dinitrophenyl (DNP) IgE. Moreover, sulfapyridine inhibited histamine release dose-dependently in the rat peritoneal mast cells (RPMC) activated by compound 48/80 or anti-DNP IgE. When sulfapyridine was added, the level of cAMP in RPMC, transiently and significantly increased about 4-fold compared with that of basal cells. These results indicate that sulfapyridine inhibits mast cell-mediated immediate-type allergic reactions in vivo and in vitro.

Effects of sulfasalazine and its metabolites on steady state messenger RNA concentrations for inflammatory cytokines, matrix metalloproteinases, and tissue inhibitors of metalloproteinase in rheumatoid synovial fibroblasts

OBJECTIVE

To determine the effects of sulfasalazine (SASP) and its metabolites sulfapyridine (SP) and 5-amino salicylic acid (5ASA) on steady state mRNA levels of inflammatory cytokines [interleukin 1beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha)], matrix metalloproteinases [collagenase (MMP1), stromelysin (MMP3), gelatinase 72 kDa (MMP2)], tissue inhibitors of metalloproteinase (TIMP 1 and TIMP 2), and the TNF-alpha receptor in rheumatoid synovial fibroblasts.

METHODS

Cells were dosed with each compound for 24 h in the presence or absence of PMA inducer and messenger RNA (mRNA) extracted and subjected to Northern blot analysis. Messenger RNA levels were quantitated by densitometry and normalized to GAPDH or 18S rRNA.

RESULTS

We observed some modest effects of sulfasalazine and its metabolites on steady state mRNA levels including: (1) repressed mRNA levels for TNF-alpha [approximately 40% with 3x (drug median serum concentration) all 3 drugs], stromelysin (approximately 24% with 3x all 3 drugs and approximately 31% with 3x 5ASA), and collagenase (approximately 27% with 3x 5ASA); (2) elevated mRNA levels for TIMP 2 (3.5 kb transcript) (51% with 3x SP and 44% with 3x 5ASA), gelatinase (approximately 20% with 3x SP and 3x 5ASA), stromelysin (approximately 40% with 3x and 1x SASP), IL-1beta (approximately 31% with 0.1x 5ASA); and (3) no effect on mRNA levels for TNF-alpha receptor and TIMP 1.

CONCLUSION

(1) SASP and its metabolites showed varied effects on steady state mRNA concentrations for gene transcripts that fell into 3 categories: (a) repressed, (b) elevated, (c) no effect on mRNA levels. (2) No apparent linear dose response effect was observed for SASP or its metabolites, although a generalized suppression of mRNA levels at all doses was seen in some cases. (3) No predominant suppressive effect (> or = 50%) of mRNA levels by any of the drugs was observed for any of the genes studied; however, TIMP 2 mRNA levels increased 51% with 3x SP and 44% with 3x 5ASA.

Inhibition of nuclear factor kappa B and induction of apoptosis in T-lymphocytes by sulfasalazine

1. Chronic inflammatory diseases have been shown to be associated with NF-kappaB activation and impaired apoptosis of immune cells. The aim of the present study was to investigate if sulfasalazine and its colonic metabolites 5-aminosalicylic acid (5ASA) and sulfapyridine affect NF-kappaB/Rel activation and viability of T-lymphocytes. 2. Sulfasalazine inhibits NF-kappaB/Rel activation in the murine T-lymphocyte cell line RBL5 using electrophoretic mobility shift assays. In transfection assays sulfasalazine treatment for 4 h inhibits kappaB-dependent transcription with an IC50 value of approximately 0.625 mM. 3. Higher doses or prolonged treatment result in cell death of T-lymphocytes in a dose- and time-dependent manner. Cell death is caused by apoptosis as judged by DNA fragmentation, annexin V and Apo 2.7 staining. Induction of apoptosis is a fast event with 50% apoptotic cells after a 4 h incubation with 2.5 mM sulfasalazine. The ED50 value for apoptosis induction after 24 h treatment was approximately 0.625 mM. 4. In contrast, 5ASA and sulfapyridine neither inhibit NF-kappaB/Rel activation nor induce apoptosis in T-lymphocytes at doses up to 5.0 mM. 5. These results demonstrate that sulfasalazine, but not 5ASA or sulfapyridine, strongly inhibits NF-kappaB activation and potently induces apoptosis in T-lymphocytes. Inhibition of NF-kappaB/Rel activation and subsequent clearance of activated T-lymphocytes by apoptosis might thus explain the beneficial effects of sulfasalazine in the treatment of chronic inflammatory disorders.

Effects of sulphapyridine on sperm transport through the rat epididymis and contractility of the epididymal duct

This study was undertaken to investigate the effects of sulphapyridine on the transport of spermatozoa through different regions of the epididymis and on the contractility of the epididymal duct in the rat. Sperm transport was investigated by labelling testicular spermatozoa with [3H]thymidine and measuring intraluminal pressures of the epididymis by micropuncture, using a servo-nulling pressure transducer system. In control rats, the transit times of epididymal spermatozoa from the initial segment to the caput, from the caput to the proximal cauda, and from the proximal cauda to the distal cauda were 2, 6 and 3 days, respectively, giving a total transit time of 11 days. The total transit time was shortened to 8 days after treatment with sulphapyridine at a dosage of 450 mg kg-1 for 38-52 days. The rate of sperm transport was most affected in the caput epididymidis. Measurements of intraluminal pressures showed that sulphapyridine had no effect on spontaneous contractions in any regions of the epididymis. However, the frequency of contraction of the corpus and cauda epididymides in response to administration of 10 micrograms noradrenaline kg-1 in the sulphapyridine-treated rats was significantly higher (P < 0.05) than it was in the controls. Methacholine, at a dose of 20 micrograms kg-1, produced a smaller increase in basal pressure in the caput epididymidis of sulphapyridine-treated rats (P < 0.05) compared with controls. The results led to the conclusion that sulphapyridine increases the rate of sperm transport from the caput through the cauda epididymidis, in part, by changes in the responsiveness of the epididymis to the autonomic nervous system.

Treatment with sulfasalazine or sulfapyridine, but not 5-aminosalicyclic acid, inhibits basic fibroblast growth factor-induced endothelial cell chemotaxis

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by leukocyte recruitment and angiogenesis. We investigated the effects of sulfasalazine (SSZ) and its metabolites, sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA), on components of angiogenesis, namely, endothelial cell (EC) chemotaxis and proliferation, as well as on EC chemokine and soluble adhesion molecule expression.

METHODS

SSZ, SP, and 5-ASA were assayed for their effects on basic fibroblast growth factor (bFGF)-induced human dermal microvascular endothelial cell (HMVEC) chemotaxis and proliferation. EC were plated on Matrigel to assess the effect of SSZ on EC tube formation. Enzyme-linked immunosorbent assays were performed to determine changes in HMVEC production of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), growth-related oncogene alpha (GROalpha), epithelial neutrophil-activating peptide 78 (ENA-78), soluble E-selectin (sE-selectin), and soluble intercellular adhesion molecule 1 (sICAM-1) upon treatment with SSZ or its metabolites.

RESULTS

HMVEC incubated with SSZ or SP exhibited reduced bFGF-induced chemotaxis (59%, [n = 7] and 22%, [n = 3], respectively) (P<0.05). SSZ and SP decreased basal HMVEC proliferation, while 5-ASA increased proliferation (P<0.05; [n = 5]). SSZ decreased bFGF-induced HMVEC proliferation (P<0.05 [n = 5]). SSZ inhibited phorbol 12-myristate 13-acetate-induced HMVEC tube formation (P<0.05; [minimum n = 5]). Tumor necrosis factor alpha-stimulated HMVEC shedding of sICAM-1 was reduced by incubation with either SSZ (19%) or 5-ASA (23%) (P<0.05; [n = 6]). SP inhibited cytokine-stimulated HMVEC expression of IL-8 and MCP-1 (P<0.05; [n = 4]). Neither SSZ nor its metabolites had any effect on HMVEC production of sE-selectin, GROalpha, or ENA-78.

CONCLUSION

These results demonstrate that SSZ and its metabolite SP may affect the pathogenesis of RA by inhibiting EC chemotaxis, proliferation, tube formation, and expression of sICAM-1, IL-8, and MCP-1.

Effects of BX661A, a new therapeutic agent for ulcerative colitis, on chemotaxis and reactive oxygen species production in polymorphonuclear leukocytes in comparison with salazosulfapyridine and its metabolite sulfapyridine

5-[4-(2-Carboxyethylcarbamoyl)phenylazo]salicylic acid disodium salt dihydrate (CAS 80573-04-2, BX661A) is developed as a therapeutic agent for ulcerative colitis. To clarify the mechanisms of action of BX661A, the effects of BX661A and its metabolites 5-aminosalicylic acid (5-ASA) and 4-aminobenzoyl-beta-aline (4-ABA) on polymorphonuclear (PMN) leukocyte chemotaxis and production of reactive oxygen species (ROS) from PMN cells were investigated and compared with the effects of 2-hydroxy-5-[[4-[(2-pyridinylamino)sulfonyl]phenyl]azo]-benzoic acid (CAS 599-79-1, SASP) and its metabolite 4-amino-N-2-pyridinyl-benzenesulfonamide (CAS 144-83-2, SP). 1. BX661A, SASP and SP concentration-dependently inhibited guinea pig PMN cell chemotaxis induced by zymosan-activated serum (IC50 = 1.39, 2.17 mmol/l, respectively) and by N-formyl-methionyl-leucyl-phenylalanine (FMLP) with IC50 values of 0.55, 0.06 and 0.66 mmol/l, respectively. 5-ASA and 4-ABA weakly affected the PMN cell chemotaxis induced by zymosan-activated serum (both IC50 values > or = 10 mmol/l) and by FMLP (IC50 > or = 10 and 8.05 mmol/l, respectively). 2. BX661A, SASP and SP concentration-dependently inhibited human PMN cell chemotaxis induced by FMLP with IC50 values of 0.68, 0.05 and 2.68 mmol/l, respectively, but both IC50 values of 5-ASA and 4-ABA were > 10 mmol/l. 3. BX661A, SASP, 5-ASA, 4-ABA and SP inhibited ROS production from rat PMN cells stimulated by FMLP in a concentration-dependent manner (IC50 = 58.4, 27.5, 0.61, 1242 and 13.9 mmol/l, respectively). 4. BX661A, SASP, 5-ASA, 4-ABA and SP inhibited ROS production from human PMN cells stimulated by FMLP in a concentration-dependent manner (IC50 = 67.4, 46.1, 0.69, 748 and 8.31 mumol/l, respectively). These results suggest that BX661A itself has inhibitory effects against PMN cell chemotaxis and ROS production from PMNs and that 5-ASA, which is the active moiety of BX661A, has a potent inhibitory effect against ROS production from PMNs. Therefore, these effects may be partially involved in the therapeutic effects of BX661A on ulcerative colitis.

Determination of the active moiety of BX661A, a new therapeutic agent for ulcerative colitis, by studying its therapeutic effects on ulcerative colitis induced by dextran sulfate sodium in rats

5-[4-(2-Carboxyethylcarbamoyl)phenylazo]salicylic acid disodium salt dihydrate (CAS 80573-04-2, BX661A) is being developed as a therapeutic drug for ulcerative colitis. To determine the active therapeutic moiety of BX661A, the therapeutic effects with single and combined administration of 5-aminosalicylic acid (5-ASA), 4-aminobenzoyl-beta-alanine (4-ABA) and 4-amino-N-2-pyridinyl-benzenesulfonamide (CAS 144-83-2, sulfapyridine, SP) on ulcerative colitis induced by dextran sulfate sodium (DSS) in rats were investigated, and the following results were obtained. 1. BX661A at doses of 30, 100 and 300 mg/kg (p.o.) dose-dependently decreased the erosion area (mm2) in the large intestine with % inhibition values of 28.7, 49.1 and 61.6%, and the shortening of the large intestine with % inhibition values of 17.1, 25.7 and 48.6%, respectively. Salazosulfapyridine (SASP) at doses of 30 and 100 mg/kg (p.o.) decreased the erosion area (mm2) in the large intestine with % inhibition values of 30.7 and 45.3%, respectively, but did not improve the shortening of the large intestine. However, at a dose of 300 mg/kg (p.o.) SASP, the % inhibition value of the erosion area in the large intestine was reduced. 2. A single intrarectal administration of 5-ASA (105 mg/kg, i.r.) significantly decreased the erosion area (mm2) in the large intestine, but a single administration of 4-ABA or SP did not show any significant effect on the erosion area. Combined administration with 5-ASA (105 mg/kg, i.r.) and 4-ABA (142.8 mg/kg, i.r.) significantly decreased the erosion area (mm2) in the large intestine with a % inhibition value of 63.8%. On the other hand, the efficacy of 5-ASA disappeared with combined administration with SP (% inhibition value of 7.3%). These results suggest that 5-ASA is the active moiety for the therapeutic effects of BX661A and indicate that the efficacy of 5-ASA disappears with the combined use of SP, but not of 4-ABA. Therefore, it seems that BX661A is clinically safe and more effective than SASP in the treatment of patients with ulcerative colitis.

Effects of BX661A, a new therapeutic agent for ulcerative colitis, on reactive oxygen species in comparison with salazosulfapyridine and its metabolite sulfapyridine

5-[4-(2-Carboxyethylcarbamoyl)phenylazo]salicylic acid disodium salt dihydrate (CAS 80573-04-2, BX661A) is developed as a therapeutic agent for ulcerative colitis. To clarify its mechanism of action, the effects of BX661A and its metabolites 5-aminosalicylic acid (5-ASA) and 4-aminobenzoyl-beta-alanine (4-ABA) on reactive oxygen species: superoxide radicals (O2-) generated by hypoxanthine and xanthine oxidase, hydrogen peroxide (H2O2), hypochlorite radicals (OCl-) and hydroxyl radicals (OH.), were investigated and compared with the effects of 2-hydroxy-5-[[4-[(2-pyridinylamino)sulfonyl]phenyl]azo]-benzoic acid (CAS 599-79-1, salazosulfapyridine, SASP) and its metabolite 4-amino-N-2-pyridinyl-benzenesulfonamide (CAS 144-83-2, sulfapyridine, SP). 1. BX661A, SASP and 5-ASA inhibited O2- radical production in a concentration-dependent manner (IC50 = 0.14, 0.13 and 0.19 mmol/l, respectively). The effects of 4-ABA and SP on O2- radical production were weak (IC50 = > 10 and > 3 mmol/l, respectively). In contrast, superoxide dismutase inhibited O2- radical production in a concentration-dependent manner (IC50 = 1.7 U/ml). 2. BX661A, SASP, 4-ABA and SP had no H2O2 scavenging effects. 5-ASA scavenged H2O2, but its maximal scavenging action was 51.3%. In contrast, catalase scavenged H2O2 in a concentration-dependent manner (IC50 = 0.47 U/ml). 3. BX661A, SASP and 5-ASA scavenged OCl- radicals in a concentration-dependent manner (IC50 = 69.5, 73.8 and 21.7 mumol/l, respectively). 4-ABA and SP had no OCl- radical scavenging effects. In contrast, nordihydroguaiaretic acid (NDGA) scavenged OCl- radicals in a concentration-dependent manner (IC50 = 8.7 mumol/l). 4. BX661A and SASP scavenged OH. radicals in a concentration-dependent manner; the maximal scavenging values were 39.5 (10 mmol/l) and 48.6% (3 mmol/l), respectively. 4-ABA and SP had no OH. radical scavenging effects. In contrast, 5-ASA scavenged OH. radical in a concentration-dependent manner (IC50 = 1.46 mmol/l). These results suggest that BX661A has O2- and OCl- radical scavenging effects and that 5-ASA has O2-, OCl- and OH. radical scavenging effects. Therefore, these effects may be partially involved in the therapeutic effects of BX661A on ulcerative colitis.

Sulfasalazine: a potent and specific inhibitor of nuclear factor kappa B

Transcription factors of the NF-kappaB/Rel family are critical for inducible expression of multiple genes involved in inflammatory responses. Sulfasalazine and its salicylate moiety 5-aminosalicylic acid are among the most effective agents for treating inflammatory bowel disease and rheumatoid arthritis. However, the mode of action of these drugs remains unclear. Here we provide evidence that the transcription factor NF-kappaB is a target of sulfasalazine-mediated immunosuppression. Treatment of SW620 colon cells with sulfasalazine inhibited TNFalpha-, LPS-, or phorbol ester- induced NF-kappaB activation. NF-kappaB-dependent transcription was inhibited by sulfasalazine at micro- to millimolar concentrations. In contrast, 5-aminosalicylic acid or sulfapyridine did not block NF-kappaB activation at all doses tested. TNFalpha-induced nuclear translocation of NF-kappaB was prevented by sulfasalazine through inhibition of IkappaBalpha degradation. When blocking proteasome-mediated degradation of IkappaBalpha, we could demonstrate that sulfasalazine interfered with IkappaBalpha phosphorylation, suggesting a direct effect on an IkappaBalpha kinase or on an upstream signal. Inhibition of NF-kappaB activation seems to be specific since other DNA-binding activities such as AP1 were not affected. These results demonstrate that sulfasalazine is a potent and specific inhibitor of NF-kappaB activation, and thus may explain some of the known biological properties of sulfasalazine.

Sulphasalazine, olsalazine and sulphapyridine induce mitogenic actions in the rat intestinal epithelium

Our aim was to study the influence of sulphasalazine (SASP), olsalazine (ADS) and sulphapyridine (SP) on the cell kinetics of the intestinal epithelium in conventional rats. Groups of rats were treated with SASP, ADS or SP for 9 days. After an intraperitoneal injection of a metaphase blocker, the rats were killed and the jejunum, ileum and colon were examined in histological sections by means of the cumulative mitotic index (MI), growth fraction and number of cells in crypts and villi. SP increased both the MI in the jejunum, ileum and colon and the number of crypt cells (p < 0.05 vs controls). In contrast, SASP and ADS increased the MI only in the colonic epithelium (p < 0.05 vs controls). The growth fraction was essentially unaffected. Our results suggest that SASP, SP and ADS have a selective compartment-dependent proliferative action on the epithelium of the intestinal tract.

The effect of sulphasalazine on neutrophil superoxide generation in rheumatoid arthritis

The production of superoxide by the peripheral blood neutrophils of 19 patients with active rheumatoid arthritis was measured during treatment with sulphasalazine (SASP). The response to drug treatment was determined by change in plasma viscosity, CRP, early morning stiffness and articular index over a 10-point scale. Of the 19 patients studied, eight were considered to have responded well to SASP and seven to have responded poorly or not at all. Over the treatment period, plateau levels of superoxide production fell in seven of the eight responders (P = 0.028) compared with a non-significant fall in 3/7 of the non-responder groups. The initial rate of superoxide production also fell in the responder group, but this was not statistically significant. Initial values in both the responder and non-responder groups were comparable with those seen for normal controls. Analysis of drug levels showed all patients to be compliant with drug treatment; however, drug levels and neutrophil activity were not correlated. Studies of the effect of SASP and sulphapyridine on superoxide production in vitro showed no difference between good and poor responders. These results suggest that there is no inherent difference between good and poor responders regarding the susceptibility of their neutrophils to SASP. SASP's action on neutrophils, therefore, appears not to be its main mechanism of disease-modifying activity in RA.

Effect of methotrexate and sulphasalazine on UMR 106 rat osteosarcoma cells

Methotrexate is commonly used in the treatment of rheumatoid arthritis. An osteopathy has been described in children treated with methotrexate for leukaemia, consisting of bone pain, osteoporosis and fractures. Animals given short-term high-dose and long-term low-dose methotrexate have both reduced bone formation and increased resorption on histomorphometry. As patients with rheumatic diseases have numerous risk factors for osteoporosis, possible additional risk from low-dose methotrexate is of relevance to the rheumatologist. To investigate further the mechanism of osteoporosis in animals and man, in vitro studies were carried out on an osteoblast cell line, using concentrations found in patients with rheumatic disease. UMR 106 rat osteoblast-like osteosarcoma cells were incubated with methotrexate, and also with sulphasalazine, an anti-rheumatic drug with no known effect on bone, for comparison. A dose-dependent toxic effect of methotrexate on the cell line was observed using concentrations found in patients with rheumatic disease. This was not observed with sulphasalazine. The reduced bone formation observed in animals and man may be due to a direct effect of methotrexate on the osteoblast.

Which is the active moiety of sulfasalazine in ankylosing spondylitis? A randomized, controlled study

OBJECTIVE

To compare the efficacy of sulfasalazine (SSZ) with its two moieties, 5-aminosalicylic acid (ASA) and sulfapyridine (SP), in patients with active ankylosing spondylitis (AS).

METHODS

A 26-week randomized, observer-blinded, 2-center, controlled study of treatment with either SSZ, ASA, or SP was conducted in 90 patients with active AS. Patients were evaluated at baseline and at monthly intervals, using several clinical and laboratory measures of disease activity. A global assessment of treatment efficacy was made by both patients and observers at the end of the study period.

RESULTS

There were no significant changes in any of the parameters of disease activity in the ASA treatment group. Levels of serum IgG, IgA, and IgM fell significantly during treatment with SP, but none of the other changes reached statistical significance. Plasma viscosity and IgG and IgA levels fell significantly during treatment with SSZ, as did nocturnal spinal pain and overall spinal pain. Patients and observers reported a favorable outcome after treatment with SSZ or SP significantly more often than with ASA treatment.

CONCLUSION

SP appears to be the active moiety in AS, although there was a trend suggesting a better outcome in the SSZ group compared with the SP group, perhaps suggesting the importance of a common sulfonamide structure for efficacy.

The effects of aminosalicylic acid derivatives on nitric oxide in a cell-free system

AIMS AND METHODS

To determine the effect of aminosalicylic acid derivatives on the concentration of nitric oxide produced in a cell-free system, by the use of a sensitive and specific polarographic meter.

RESULTS

The aminosalicylic acid derivatives 3-ASA (IC50 100 microM), 4-ASA (IC50 350 microM) and 5-ASA (IC50 5 microM) all decreased the nitric oxide signal. These drugs had a similar inhibitory effect on the formation in vitro of nitrite from sodium nitroprusside (IC50: 200 microM, 500 microM and 100 microM, respectively). Sulphasalazine (31.1 +/- 5% decrease in signal at 1 mM) was less effective than 5-ASA, but sulphapyridine, N-acetyl 5-ASA, indomethacin and hydrocortisone produced no decrease in nitric oxide signal at all.

CONCLUSIONS

Nitric oxide binding may be part of the mechanism by which ASA derivatives exert their therapeutic effect, and this work suggests that it may be an important factor in the pathogenesis of ulcerative colitis.

Modulation of cytokine release from human monocytes by drugs used in the therapy of inflammatory bowel diseases

BACKGROUND

Cytokines produced in the gut mucosa play an important role in the pathogenesis of inflammatory bowel diseases (IBD). To determine whether drugs used in the treatment of these diseases modulate cytokine synthesis, we investigated their effects on endotoxin-induced tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 beta and IL-6 release by elutriation-purified human monocytes in vitro.

METHODS

Drugs tested were dexamethasone, 5-aminosalicylic acid, sulphapyridine and zileuton (a 5-lipoxygenase inhibitor). Monocytes were isolated and stimulated with endotoxin, and TNF, IL-1 and IL-6 levels were determined using an enzyme-linked immunosorbent assay.

RESULTS

Monocyte stimulation with endotoxin resulted in an average TNF release of 2464 +/- 64 pg/10(6) cells, IL-1 release of 616 +/- 47 pg/10(6) cells and IL-6 release of 2259 +/- 148 pg/10(6) cells. Addition of dexamethasone resulted in a reduction of TNF, IL-1 and IL-6 release to below background levels. Sulphapyridine significantly reduced TNF and induced IL-1 release in a dose-dependent fashion, but had no significant effect on IL-6 release. 5-Aminosalicylic acid did not modulate IL-6 synthesis, but significantly reduced IL-1 and enhanced TNF synthesis. Zileuton reduced TNF and IL-6 release, but enhanced IL-1 release.

CONCLUSION

We conclude that these anti-inflammatory drugs are able to modulate cytokine release by human monocytes. Further studies are needed to determine whether these effects are related to their therapeutic efficacy in IBD.

Sulphasalazine inhibition of thiopurine methyltransferase: possible mechanism for interaction with 6-mercaptopurine and azathioprine

Thiopurine drugs are used in the treatment of inflammatory bowel disease--as are sulphasalazine and its metabolite 5-aminosalicylic acid (ASA). S-Methylation catalyzed by thiopurine methyltransferase (TPMT) is a major pathway in the metabolism of thiopurines. The hypothesis was tested that TPMT might be inhibited by sulphasalazine or isomers of ASA. Sulphasalazine as well as 3-, 4- and 5-ASA inhibited recombinant human TPMT, with IC50 values of 78, 99, 2600 and 1240 microM, respectively. Kinetic studies demonstrated that the inhibition of TPMT by sulphasalazine and ASA isomers was non-competitive with regard to the thiopurine substrate, 6-MP, and was uncompetitive with regard to the methyl donor for the reaction, S-adenosyl-L-methionine. Our observations raise the possibility of a clinically significant drug-drug interaction in patients treated simultaneously with sulphasalazine and thiopurine drugs.

Sulphonamides as anti-inflammatory agents: old drugs for new therapeutic strategies in neutrophilic inflammation?

1. It is well known that neutrophils act as mediators of tissue injury in a variety of inflammatory diseases. Their histotoxic activity is presently thought to involve proteinases and oxidants, primarily hypochlorous acid (HOCl). This oxidant is also capable of inactivating the specific inhibitor of neutrophil elastase (alpha 1-antitrypsin), thereby favouring digestion of the connective matrix. 2. In the present work, we found that sulphanilamide and some sulphanilamide-related anti-inflammatory drugs such as dapsone, nimesulide and sulphapyridine reduce the availability of HOCl in the extracellular microenvironment of activated neutrophils and prevent the inactivation of alpha 1-antitrypsin by these cells in a dose-dependent manner. The ability of each drug to prevent alpha 1-antitrypsin from inactivation by neutrophils correlates significantly with its capacity to reduce the recovery of HOCl from neutrophils. Five other non-steroidal anti-inflammatory drugs were completely ineffective. 3. Therefore, sulphanilamide-related drugs, i.e. dapsone, nimesulide and sulphapyridine, have the potential to reduce the bioavailability of neutrophil-derived HOCl and, in turn, to favour the alpha 1-antitrypsin-dependent control of neutrophil elastolytic activity. These drugs appear as a well-defined group of agents which are particularly prone to attenuate neutrophil histotoxicity. They can also be viewed as a previously unrecognized starting point for the development of new compounds in order to plan rational therapeutic strategies for controlling tissue injury during neutrophilic inflammation.

5-Aminosalicylic acid abrogates T-cell proliferation by blocking interleukin-2 production in peripheral blood mononuclear cells

The antiinflammatory agent sulfasalazine (SS) is prescribed to treat Crohn's disease, ulcerative colitis and rheumatoid arthritis. Activated T cells are present within diseased mucosal and synovial sites. We tested whether SS or its metabolites 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP) inhibited the T-cell activation products interleukin 2 (IL-2) and interleukin 2 receptor alpha-chain (IL-2R alpha). Experiments were performed in phytohemaglutinin- and phorbol ester-stimulated peripheral blood mononuclear cells. Radioactive thymidine and leucine incorporation assayed DNA and protein synthesis, respectively. Enzyme-linked immunosorbent assay and Northern blot analysis measured IL-2 and IL-2R alpha. Lactate dehydrogenase release determined cell viability, and intracellular free calcium was measured by an indole fluorescent indicator. SS and 5-ASA, but not SP, inhibited T-cell proliferation and protein synthesis in phytohemaglutinin- and phorbol ester-stimulated peripheral blood monomuclear cells. 5-ASA (625 microM) markedly reduced culture supernatant IL-2 protein levels by 92% and steady-state IL-2 messenger RNA levels 4.4-fold at 24 and 18 hr, respectively. The supplementation of IL-2 restored T-cell proliferation only in 5-ASA-treated cultures. SS, 5-ASA and SP did not alter intracellular calcium accumulation after mitogenic stimulation. SS and 5-ASA (625 microM) caused 71% and 37% cytotoxicity, respectively, in 72-hr cultures. 5-ASA inhibits T-cell proliferation in part by blocking IL-2 messenger RNA accumulation and protein production downstream of the rise in cytosolic calcium. Inhibition of IL-2 production is an additional mechanism of action for 5-ASA.

Effect of 5-aminosalicylic acid and analogous substances on superoxide generation and intracellular free calcium in human neutrophilic granulocytes

Activated polymorphonuclear leukocytes (PMNs), which are found in the inflammatory lesions of chronic inflammatory bowel disease, produce tissue-destructive oxygen-derived free radicals. The influence of 5-aminosalicylic acid (5-ASA), its acetylated metabolite (Ac-5-ASA), sulfasalazine (SAZ), and olsalazine (OLZ) (5-ASA dimer linked by an azo group) in pharmacologically relevant concentrations (0.1-10 mM) were tested on PMN superoxide production with either the receptor-specific agent formyl-methionyl-leucyl-phenylalanine (fMLP) or the protein kinase C activator phorbol myristate acetate (PMA). Inhibition of receptor-specific superoxide production occurred at 0.07, 0.32, and 0.63 mM (IC50 values) for 5-ASA, SAZ, and OLZ, respectively. No inhibitory effects of SAZ and OLZ were observed when PMA was applied as stimulus for PMN superoxide production. The results indicate that the signal to which PMNs respond by generating superoxide is primarily due to calcium release from intracellular stores. They further suggest that SAZ and OLZ may affect the oxygen-derived free radical production in human PMNs by unspecific cytotoxicity or by interference with the nicotinamide adenine dinucleotide phosphate, reduced (NADPH) oxidase system, whereas 5-ASA itself is a free radical scavenger.

Comparison of the effect of oral sulphasalazine, sulphapyridine and 5-amino-salicylic acid on the in vivo antibody response to oral and systemic antigen

1. Mice, whose drinking water contained sulphasalazine, sulphapyridine or 5-amino-salicylic acid, received an antigenic challenge by cholera toxin administered either orally or systemically. 2. Sulphasalazine treated mice made less specific antibody of IgA class provided the antigen also was administered orally (P = 0.009 for days 7-28). When the antigen was administered systemically, there was a vigorous anti-cholera toxin antibody response of IgG class, and a lesser IgM but only a weak IgA response. The effect of sulphasalazine in this case was confined to the IgG response, which was significantly suppressed on day 28 (P = 0.008). 3. Sulphapyridine and 5-amino salicylic acid had no significant effect on the anti-cholera toxin (CT) responses of all three classes. 4. It therefore appears that in this model, only sulphasalazine is capable of influencing the humoral immune system, the antibody class affected depending on the route of entry of antigen. This may have implications for conditions such as rheumatoid arthritis and chronic inflammatory bowel disease, for which sulphasalazine has been found useful.

Sulphasalazine inhibition of human granulocyte activation by inhibition of second messenger compounds

The effects of sulphasalazine on the production of second messenger compounds in human granulocytes have been characterised by various stimuli. The increases in cytosolic calcium, inositol trisphosphate, diacylglycerol, and phosphatidic acid (all important mediators of intracellular signal transduction) triggered by stimulation were inhibited by sulphasalazine. The metabolites 5-amino-salicylic acid and sulphapyridine were less potent inhibitors than the mother compound. It is concluded that sulphasalazine inhibits the synthesis of phosphoinositide derived second messenger compounds at the level of phospholipase C or its regulatory guanosine 5'-triphosphate (GTP) binding protein. Inhibition of phosphatidic acid synthesis was either due to the same mechanism, or to interaction with a phospholipase D regulating GTP binding protein.

Induction of kinetochore positive and negative micronuclei in mouse bone marrow cells by salicylazosulfapyridine and sulfapyridine

Salicylazosulfapyridine (SASP) and its major metabolite sulfapyridine (SP) have been shown to induce chromosomal damage in vivo. Both chemicals were tested in the micronucleus (MN)/kinetochore (KC) staining test to gain insight into the question of whether chromosomal breakage, aneuploidy-inducing events, or both were important to the observed production of MN in bone marrow cells of mice. In this test, both SASP and SP were shown to be strong inducers of kinetochore positive (KC+) MN. Although small increases in kinetochore negative (KC-) MN were also observed in SP treated mice, as well as in mice receiving the highest dose of SASP tested, the results suggest that both chemicals induce predominantly aneuploidogenic type damage.

Induction of chromosomal damage in mammalian cells in vitro and in vivo by sulfapyridine or 5-aminosalicylic acid

Sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA) are the two primary metabolites of the anti-inflammatory drug salicylazosulfapyridine (SASP). These two metabolites were studied for induction of chromosomal damage in mammalian cells, in vitro and in vivo, in an attempt to understand better the genetic effects produced by SASP in humans and laboratory mice. To this end, SP and 5-ASA were tested for induction of sister-chromatid exchanges (SCE) and chromosomal aberrations (Abs) in Chinese hamster ovary (CHO) cells in vitro. In addition, they were tested in vivo for induction of micronuclei (MN) in mouse bone marrow polychromatic erythrocytes (PCE). SP gave positive results in the in vitro SCE test and the in vivo MN test, and negative results in the in vitro Abs test. 5-ASA was negative in all three tests. These results indicate that it is the SP metabolite of SASP that is necessary for the induction of chromosomal damage reported to occur in humans and mice after treatment with SASP.

Effect of aminophenols (5-ASA and 4-ASA) on colonic interleukin-1 generation

The effect of 5-ASA and 4-ASA, drugs used for the treatment of inflammatory bowel disease, on modulation of experimental colitis and on colonic generation of interleukin-1 was evaluated. Three weeks of treatment with 5-ASA or 4-ASA (50 micrograms/kg) and one week of treatment with 5-ASA significantly decreased colonic interleukin-1 generation and the extent and severity of inflammation in a rat model of colitis induced by trinitrobenzene sulphonic acid. Colonic biopsies were obtained from patients with active ulcerative colitis and organ cultured 24 hours in the absence or presence of the following drugs: sulphasalazine, sulphapyridine, 5-ASA and 4-ASA (25-100 micrograms/ml). Interleukin-1 content in tissue cultured in the presence of 5-ASA (100 micrograms/ml) was two-thirds of its content in tissue cultured in drug free medium and its release into the medium was decreased by 50%. Sulphasalazine 50 micrograms/ml significantly decreased by 33% the tissue content but did not affect interleukin-1 release and a higher dose was not more effective. Sulphapyridine and 4-ASA in doses up to 100 micrograms/ml did not affect either interleukin-1 colonic content or its release into the culture medium. We conclude that pharmacological suppression of colonic interleukin-1 generation may be one, although not the sole mechanism to explain the therapeutic efficacy of 5-ASA in the treatment of inflammatory bowel disease.

Dapsone suppresses integrin-mediated neutrophil adherence function

The anti-inflammatory influence of dapsone may involve suppression of neutrophil chemotaxis to selected attractants, but other actions of the drug are likely also involved. We have discovered that dapsone may suppress migration of neutrophils to extravascular sites through inhibition of adherence functions required for neutrophil recruitment. Neutrophil adherence mediated by integrins (CD11/CD18 or Mac-1 family receptors) was measured in vitro in terms of binding of stimulated cells to albumin-coated wells of microtiter plates, using phorbol myristate acetate (PMA) and N-formylmethionyl-leucyl-phenylalanine (FMLP) as stimuli. Adherence was assessed by staining attached cells with crystal violet dye and measuring the dye concentration at OD590 using an automated plate reader. The role of integrins in this assay was confirmed by the ability of anti-integrin antibody to suppress stimulated neutrophil adherence. The OD590 value for cells adhering to albumin in the absence of stimulus and dapsone averaged 0.2 +/- 0.04 (SEM) over five experiments. In the presence of 0.1 microM PMA or 10(-6) M FMLP, the OD590 values averaged 0.88 +/- 0.1 and 0.75 +/- 0.12, respectively. Dapsone did not affect unstimulated neutrophil adherence but, when present with stimulus, produced a dose-related inhibitory effect on adherence. Fifty percent inhibitory doses were approximately 150 micrograms/ml dapsone for both stimuli. Sulfapyridine reproduced the inhibitory effect of dapsone, but two structurally related compounds, hydrochlorothiazide and furosamide, did not. The observed ability of dapsone to inhibit neutrophil chemotaxis under agarose to FMLP and interleukin-8 may also be explained by interference with integrin-mediated adherence required for motility in this assay system. To consider if dapsone might have a similar inhibitory influence on neutrophil adherence in vivo, we tested the stimulated adherence function of neutrophils isolated from three individuals on dapsone therapy for dermatitis herpetiformis. Stimulated adherence of patients' cells averaged less than 40 percent of the control value. Suppression of leukocyte integrin function may therefore also contribute to the ability of dapsone to inhibit neutrophil infiltration in neutrophilic dermatoses.

The effect of sulfasalazine on bovine endothelial cell proliferation and cell cycle phase distribution. Comparison with olsalazine, 5-aminosalicylic acid, and sulfapyridine

Sulfasalazine is used in the treatment of chronic inflammatory states, for example, in inflammatory bowel disease and to a lesser degree in rheumatoid arthritis. In chronic inflammation, the formation of new blood vessels may play a key role in maintaining the inflammatory state. This process is dependent on the activation and proliferation of the endothelial cells. To investigate the possible role of sulfasalazine and its metabolites, sulfapyridine and 5-aminosalicylic acid, we examined the effect of these drugs on vascular endothelial cell proliferation in vitro. Cultures of bovine aortic endothelial cells were incubated with sulfasalazine and its metabolites. At 24 hours of incubation, sulfasalazine inhibited tritiated thymidine incorporation and cell proliferation and had already slowed S-phase progression at a concentration greater than 0.125 mmol/L. After 3 hours of incubation, sulfasalazine inhibition of tritiated thymidine incorporation into the DNA of endothelial cells was observed. This inhibition was completely reversible 24 hours after the drug was removed. One of the possible mechanisms for the inhibition of endothelial cell proliferation is interference with the de novo synthesis of thymidine that depends on folate-dependent enzymes. The effect of deoxyuridine and tetrahydrofolate on tritiated thymidine incorporation into cellular DNA, as well as release of tritium to water by [5-3H]-labeled deoxyuridine on methylation to thymidine, were used as probes for the de novo synthesis of thymidine. Deoxyuridine and tetrahydrofolate, when added to cells either individually or together for 3 hours, suppressed incorporation of tritiated thymidine into DNA through an increase in de novo thymidine synthesis. Sulfasalazine, but not its metabolites, reduced this suppression.2+ culture is inhibited by sulfasalazine and olsalazine but not by their metabolites. This inhibition appears to depend partly on the reduction of de novo synthesis of thymidine that is folate dependent.

Effects of sulphasalazine and its metabolites on neutrophil chemotaxis, superoxide production, degranulation and translocation of cytochrome b-245

This study describes effects of sulphasalazine, 5-amino-salicylic acid (5-ASA) and sulphapyridine on polymorphonuclear neutrophils. Chemotaxis by polymorphonuclear neutrophils incubated with 5-ASA was reduced in a concentration dependent fashion (10(-5)-10(-4) M). Degranulation and release of lysozyme and beta-glucuronidase by activated polymorphonuclear neutrophils was inhibited by sulphasalazine but inhibited by sulphasalazine (IC50: 2 x 10(-4) M) and to a lesser extent by 5-ASA (IC50: 10(-3) M). Using a cell-free system sulphasalazine was found to be a strong scavenger and 5-ASA and sulphapyridine had only weak effects. Superoxide anion production requires translocation of a cytochrome b-245 and this translocation was reduced by sulphasalazine (P less than 0.01) but not by 5-ASA or sulphapyridine. In conclusion, the intact sulphasalazine molecule has an action of its own and marked differences exist between the action of sulphasalazine and 5-ASA, which may be important for the clinical activity.

Effect of sulphapyridine on male fertility in the rat

Male rats administered sulphapyridine (60, 120 and 250 mg/kg) for 60 days demonstrated no change in body weight and testicular weight. However, there was a decrease in the weight of the epididymis. Motility and sperm reserves were reduced and were evident from fewer implantation sites and number of pregnancies. Furthermore, sulphapyridine did not show any effect on the histoarchitecture of the testis or epididymis. Serum levels of testosterone in the treated rats were comparable to their respective controls. Morphological abnormalities as revealed by scanning electron microscopic studies clearly demonstrated the detrimental effects of the drug.

Antifertility effects of sulfapyridine on male hamsters

Sulfapyridine was administered to mature male golden hamsters either by impregnation in feed pellets, or by subcutaneous injection as a solution in dimethylsulfoxide. The average litter size for control males was 8.3 +/- 3.3 (n = 13) vs. 4.2 +/- 2.7 (n = 11) for sulfapyridine-fed treated animals. Histology of the testis and epididymis was normal and sperm were normal in morphology and motility. Subcutaneous injection of sulfapyridine caused much more dramatic inhibition of male fertility than was achieved by feeding the drug. Sulfapyridine (750 mg/kg body weight in 0.2 ml DMSO) injected subcutaneously for 60 days was effective in reducing testis size and sperm quality. Histology of testes showed spermatogenic arrest at young spermatids. Two classes of animals were found in both sulfapyridine-fed and -injected treatment groups. One class was relatively resistant to the antifertility effects of the drugs. This difference may reflect differing abilities of the animals to convert sulfapyridine to an active form or to excrete its metabolites.

Effect of sulfasalazine on B cells

We studied the in vitro immunomodulatory effect of sulfasalazine on purified human B cells, using a reversed plaque forming cell (PFC) assay and a proliferation assay. Sulfasalazine inhibited the PFC response of B cells in a dose-dependent manner. Sulfasalazine was added to PFC culture systems at several time points after the cultures were started. A marked reduction in B cell response was seen in the early phases (0-48 hours). Staphylococcus Aureus Cowan I (SAC) induced maximal B cell proliferation at day 3. Sulfasalazine at 5 micrograms/ml depressed that maximal proliferation on day 3. This indicates that sulfasalazine inhibited an early-phase event in the proliferation and differentiation of B cells. Sulfapyridine also inhibited the PFC response, but 5-aminosalicylic acid and N-acetyl sulfapyridine had no significant effect. These findings are significant since sulfapyridine is an active moiety of sulfasalazine, which is responsible for the second line of defense in the treatment of rheumatoid arthritis (RA). Adding T cells or macrophages to the PFC culture system had no significant effect. Furthermore, medium containing indomethacin was used to study the effect of prostaglandin released by residual macrophages. The results indicate that sulfasalazine inhibited the PFC response without affecting T cells, macrophages or prostaglandin. Sulfasalazine apparently has a direct immunosuppressive effect on B cells.

5-Aminosalicylic acid is a potent inhibitor of interleukin 1 beta production in organ culture of colonic biopsy specimens from patients with inflammatory bowel disease

Interleukin 1 beta in biopsy specimens from inflamed colonic mucosa of patients with active inflammatory bowel disease was studied. Compared with normal colonic mucosal biopsy specimens, a significantly greater amount of interleukin 1 beta was present in rectal mucosa before (median (range) 4.3 (2.0-11.8) v 119.2 (30.1-286.8) pg/mg; p less than 0.01) and produced during organ culture (39.1 (9.4-106.8) v 97.6 (28.2-991.6) pg/mg; p less than 0.01). Values of interleukin 1 beta after culture correlated with concentrations of thromboxane B2. Organ culture of inflamed biopsy specimens in the presence of 5 aminosalicylic acid and dexamethasone reduced the amount of interleukin 1 beta detected. At the doses studied, 5 aminosalicylic acid also reduced the amount of leukotriene B4 detected after culture.

Effect of sulphasalazine and sulphapyridine on neutrophil superoxide production: role of cytosolic free calcium

As the neutrophil granulocyte plays an important part in rheumatoid inflammation the effect of sulphasalazine on neutrophil function was studied. The results show that sulphasalazine, and its metabolite sulphapyridine, inhibit neutrophil superoxide production elicited by the receptor mediated stimulus N-formyl-methionyl-leucyl-phenyl-alanine (fMLP) and by the calcium ionophore A23187. This effect seems to be dependent on inhibition of intracellular Ca++ increase as both substances reduce this increase upon cell activation with fMLP and A23187. Sulphasalazine and sulphapyridine do not inhibit superoxide production after stimulation with the ester phorbol myristate acetate, a stimulus response coupling which is independent of intracellular Ca++ increase. The reported inhibition of superoxide generation may explain, at least partly, the antirheumatic property of sulphasalazine.

Effects of sulfasalazine and a sulfasalazine analogue on the formation of lipoxygenase and cyclooxygenase products

A sulfasalazine analogue, 5'-(2,4-dichlorobenzoyl)2'-hydroxyphenylacetic acid (CL 42A), potently inhibited the formation of 5-lipoxygenase products (leukotrienes B4 and C4 and 5-hydroxyeicosatetraenoic acid) by human leukocytes. Half-maximal inhibition of leukotriene production was obtained with 5 and 10 microM CL 42A after stimulation with serum-treated zymosan or ionophore A23187, respectively. CL 42A was equipotent to nordihydroguaiaretic acid and about 50 times more potent than sulfasalazine and benoxaprofen in studies on the inhibition of LTB4 formation in leukocyte suspensions stimulated with serum-treated zymosan. Furthermore, CL 42A had no inhibitory effect on the production of 15-hydroxyeicosatetraenoic acid after incubation of human leukocytes with ionophore A23187 in the presence of exogenous arachidonic acid. Sulfasalazine inhibited the synthesis of 5-lipoxygenase products (5-hydroxyeicosatetraenoic acid and leukotriene B4: IC50 250 microM, leukotriene C4: IC50 100 microM) in a concentration-dependent manner but had no effect on 15-hydroxyeicosatetraenoic acid formation. The metabolites of sulfasalazine, sulfapyridine and 5-aminosalicylic acid, and the isomer, 4-aminosalicylic acid, were all less potent than sulfasalazine as inhibitors of leukotriene formation. Both CL 42A (IC50 20 microM) and sulfasalazine (IC50 500 microM) inhibited the synthesis of thromboxane B2 and hydroxyheptadecatrienoic acid in human platelet suspensions after arachidonic acid stimulation. However, while CL 42A inhibited cyclooxygenase, the inhibitory effect of sulfasalazine was exerted mainly on thromboxane synthase. The platelet formation of 12-hydroxyeicosatetraenoic acid was not inhibited by CL 42A whereas sulfasalazine had a weak inhibitory effect.

Sulfasalazine metabolites and dapsone attenuate formyl-methionyl-leucyl-phenylalanine-induced mucosal injury in rat ileum

The effects of 5-aminosalicylic acid (5-ASA), 4-ASA, N-acetyl-5-ASA, and sulfapyridine on mucosal permeability were determined in an experimental model of acute ileitis. In addition, the antiinflammatory drug dapsone was tested. The distal 10 cm of rat ileum was perfused with formyl-methionyl-leucyl-phenylalanine (FMLP) (10(-5) M), a bacterial peptide that activates and attracts neutrophils. Changes in mucosal permeability were assessed using the blood-to-lumen clearance of 51Cr-ethylene-diamineacetate. Luminal FMLP increased 51Cr-labeled ethylenediamineacetate clearance twofold and fourfold in the first and second hour, respectively. Addition of 5-ASA (10 mM), 4-ASA (10 mM), or dapsone (4 mM) to the luminal perfusate after 60 min of FMLP perfusion greatly attenuated the increased mucosal permeability observed after 120 min of FMLP perfusion. Neither N-acetyl-5-ASA (10 mM) nor sulfapyridine (5 mM) had an effect on the FMLP-induced increase in mucosal permeability. We characterized the inhibitory effect of these drugs on the catalytic activity of myeloperoxidase and tested their ability to scavenge hypochlorous acid in vitro. 5-Aminosalicylic acid, 4-ASA, and dapsone demonstrated a powerful inhibitory effect on the catalytic activity of myeloperoxidase, whereas all drugs were equally effective in scavenging HOCl. In additional in vitro experiments we were unable to demonstrate an inhibitory effect of either of the drugs on the catalytic activity of neutrophilic elastase. Our results indicate that inhibition of neutrophilic myeloperoxidase may be an important mechanism by which 5-ASA, 4-ASA, and dapsone attenuate FMLP-induced mucosal injury.

Inhibition of antibody secretion by 5-aminosalicylic acid

We have examined the effects of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid on antibody secretion by normal peripheral blood and intestinal mononuclear cells. Sulfasalazine and 5-aminosalicylic acid both inhibited pokeweed mitogen-stimulated secretion of immunoglobulins (Igs) A, G, and M by peripheral blood mononuclear cells in a dose-dependent manner, whereas sulfapyridine had little effect. Sulfasalazine and 5-aminosalicylic acid also inhibited spontaneous secretion of IgA by intestinal mononuclear cells, but sulfapyridine did not. Sulfasalazine inhibited pokeweed mitogen-stimulated lymphocyte proliferation, while 5-aminosalicylic acid and sulfapyridine exhibited minimal inhibition. Sulfasalazine was toxic for peripheral blood mononuclear cells, whereas 5-aminosalicylic acid and sulfapyridine were not toxic. Thus, the inhibition of antibody secretion by sulfasalazine was due to direct toxicity. On the other hand, 5-aminosalicylic acid, the therapeutically active component of sulfasalazine, was neither toxic nor antiproliferative, and appeared to exert its effects on metabolic pathways directly related to antibody synthesis. The calculated ID50 values of 5-aminosalicylic acid for antibody secretion were 1.35 mM for IgA and 1.05 mM for IgG, concentrations that are achieved in the colons of treated individuals. Indomethacin did not inhibit antibody secretion at pharmacologically relevant concentrations. 5-Aminosalicylic acid mediated inhibition of antibody secretion may play a role in inflammatory bowel disease by stopping antibody-mediated memory events involved in the induction or perpetuation of the disease process.

Role of platelet-activating factor in ulcerative colitis. Enhanced production during active disease and inhibition by sulfasalazine and prednisolone

Platelet-activating factor is released from inflammatory cells. It activates neutrophils, releases secondary messengers, and mediates mucosal ulceration and ischemia in the rat. We assessed its possible role in the pathogenesis of ulcerative colitis. Colonic biopsy specimens from patients with active ulcerative colitis and controls were incubated for 4 h in Tyrode's buffer in the presence or absence of 0.2 microM calcium ionophore (A23187) or 50 microliter of antihuman immunoglobulin E. Platelet-activating factor was determined in the tissue by aggregation assay after extraction with 80% ethanol and was confirmed by thin-layer chromatography and its inactivation by phospholipases. Platelet-activating factor was not detected in normal mucosa. Only A23187 and antihuman immunoglobulin E stimulated its activity: mean +/- SE, 43.2 +/- 8.6 and 33.0 +/- 6.1 pg/10 mg wet wt, respectively. In active ulcerative colitis basal platelet-activating factor activity was 8.9 +/- 3.5 pg/10 mg wet wt. A23187 and antihuman immunoglobulin E induced significantly higher stimulation of platelet-activating factor synthesis when compared with their effects on normal mucosa: 200 +/- 28 and 70 +/- 8.3 pg/10 mg wet wt, respectively. The enhanced stimulation induced by A23187 was dose-dependently inhibited by salazopyrine, 5-amino-salicylic acid, and prednisolone, but not by sulfapyridine. It is thus suggested that platelet-activating factor may be involved in the pathogenesis of the inflammatory response in ulcerative colitis and that its inhibition by steroids, 5-aminosalicylic acid, and salazopyrine may be an additional mechanism to explain their therapeutic effects.

Effect of sulphasalazine and its metabolites on mitogen induced transformation of lymphocytes--clues to its clinical action?

The effects of sulphasalazine (SASP), sulphapyridine (SP), and 5-aminosalicylic acid (5-ASA) have been studied on mouse spleen cells cultured in the presence of phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) and lipopolysaccharide (LPS). SASP exhibited a significant degree of suppression, at doses in the range 25-100 micrograms/ml (p less than 0.01), this suppression being greater than 50% at 50 micrograms/ml. SP exhibited only a minor degree of suppression (10% at 75 micrograms/ml, p less than 0.01). Coadministration of a non-steroidal anti-inflammatory drug (NSAID), indomethacin, produced no evidence of further suppression in the presence of SASP or SP. Administration of SP plus 5-ASA to parallel cultures that were profoundly suppressed by the molecular equivalent amount of SASP resulted in no suppression. This implied requirement of the intact parent molecule (SASP) to produce this effect, at these concentrations. The concentration of SASP required to produce more than 50% suppression was higher than that ever attained in the peripheral blood of humans receiving therapeutic doses of the drug. Human lymphocytes are similarly suppressed by SASP, but only at higher concentrations than are required for murine cells. Thus, if the parent drug is the active moiety and requires these concentrations to be effective in vivo, it follows that the site where these effects may be mediated is likely to be the intestinal tract. The effects described would suggest the gut associated lymphoid tissue as a likely target.

In vitro susceptibility of diarrhoea producing gram negative enteric bacteria to sulfasalazine, 5-aminosalicylic acid, sulfapyridine and four quinolones. Brief report

The in vitro susceptibility of diarrhoea producing Gram negative enteric bacteria to sulfasalazine, 5-aminosalicylic acid, sulfapyridine and four quinolones was investigated using an agar dilution method. All strains were resistant to 1600 micrograms/ml of sulfasalazine and 5-aminosalicylic acid. MIC range of sulfapyridine for Y. enterocolitica was 3.1-25 micrograms/ml (median:6.2) and for Salmonella 25-100 micrograms/ml (median: 100) Campylobacter jejuni/coli were less susceptible to sulfapyridine with MIC values ranging from 200 to 800 micrograms/ml. Shigella and three of five E. coli strains were resistant to 1600 micrograms/ml of sulfapyridine. Two strains of E. coli were inhibited by 25 micrograms/ml. All strains were fairly susceptible to enoxacin, ciprofloxacin, pefloxacin and ofloxacin. Cirpofloxacin was the most active drug on weight basis.

Sulfasalazine and 5-aminosalicylic acid inhibit contractile leukotriene formation

Sulfasalazine, used therapeutically in the treatment of ulcerative colitis, is cleaved in vivo to form 5-aminosalicylic acid (5-ASA) and sulfapyridine. In an isolated preparation of rat peritoneal cells both sulfasalazine (IC50 = 0.15 mM) and 5-ASA (IC50 = 2.3 mM), but not sulfapyridine, inhibited calcium ionophore-stimulated formation of contractile leukotriene activity. This activity, although not identified directly, is attributable to a mixture of leukotriene C4 and leukotriene D4 (commonly referred to as SRS-A, or slow-reacting substance of anaphylaxis). Reference compounds evinced expected activities (IC50 = 0.024 mM for phenidone, IC50 = 0.3 microM for nordihydroguaiaretic acid, IC50 = 0.033 mM for BW 755C), whereas para-aminosalicylic acid and thiosalicylic acid were inactive. These properties of sulfasalazine may contribute to its therapeutic efficacy in vivo.