On the Action of 5-Amino-Salicylic Acid and Sulfapyridine on M. avium including Subspecies paratuberculosis
Brown ST (2007) On the Action of 5-Amino-Salicylic Acid and Sulfapyridine on M. avium including Subspecies
paratuberculosis. PLoS ONE 2(6): e516. doi:10.1371/journal.pone.0000516
On the Action of 5-Amino-Salicylic Acid and Sulfapyridine on M. avium including Subspecies paratuberculosis
Robert J. Greenstein 0 1
Liya Su 0 1
Azra Shahidi 0 1
Sheldon T. Brown 0 1
0 Academic Editor: Naomi Ward, The Institute for Genomic Research , United States of America
1 1 Department of Surgery, VA Medical Center, Bronx, New York, United States of America, 2 Laboratory of Molecular Surgical Research, VA Medical Center, Bronx, New York, United States of America , 3 Microbiology , VA Medical Center, Bronx, New York, United States of America , 4 Infectious Diseases , VA Medical Center , Bronx, New York , United States of America
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 BACTECH) detection system that quantifies mycobacterial growth as arbitrary ''growth index units'' (GI). Efficacy data are presented as ''percent decrease in cumulative GI'' (%2DcGI). 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%2DcGI at 64 mg/ml), whereas sulfapyridine has virtually no effect. In contrast, against M. avium ATCC 25291, 5-ASA has no effect, whereas sulfapyridine (88%2DcGI at 4 mg/ml) is as effective as methotrexate, our positive control (88%2DcGI at 4 mg/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.
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INTRODUCTION
In 1942 sulfasalazine (Salazopyrin) was introduced into clinical
practice for ulcerative colitis. [1] Sulfasalazine has become, because
of empirically observed clinical efficacy, the most common
medicine used to treat Inflammatory Bowel Disease (IBD) [2]
with greatest efficacy in ulcerative colitis. [35]
Sulfasalazine is a conjugate of sulfapyridine and 5-
aminosalicylic acid (5-ASA.) It is cleaved into its two component molecules
following ingestion. [2] The sulfapyridine moiety [(2-(p
aminobenzenesulphonamido) pyridine] is an acknowledged antibiotic.
[6,7] However, prevailing medical dogma concludes that it is
unlikely that (sulfasalazines) antibacterial activity accounts for its
clinical efficacy. [2] In 1977, a two-week study on ulcerative
proctitis, compared 5-ASA to sulfapyridine. Because of a decrease
in inflammation in the 5-ASA group, the authors concluded, that
in the therapy of ulcerative colitis the active moiety of sulfasalazine
was 5-ASA. [8] As a consequence therapy with 5-ASA is called
anti-inflammatory although the mechanism of action of 5-ASA
in IBD is uncertain. [2]
Although controversial, there are increasingly compelling data
that all [9,10] or some of IBD may be caused by a single infectious
agent Mycobacterium avium subspecies paratuberculosis (MAP.) [913]
(& See [14] for review.) We have shown that two agents,
methotrexate and 6-mercaptopurine (6-MP) [10], presumed to have
immunomodulatory actions in IBD, [15,16] are potent
antiMAP antibiotics. We suggested that the decreases in
proinflammatory cytokines in IBD immunomodulatory therapy
might simply reflect a normal, secondary, physiological response,
as the instigating MAP infection was effectively treated. We
concluded that henceforth methotrexate and 6-MP should be
excluded from the placebo group when evaluating antiMAP
therapies in IBD. [10]
In this study we test the hypothesis that the anti-inflammatory
action of 5-ASA and/or sulfapyridine could simply be due to one
or both of sulfasalazines components acting as an antiMAP
antibiotic(s.) If correct the anti-inflammatory effect would
simply represent a normal, secondary, physiological response as
the causative MAP in (...truncated)