NOSH-aspirin: A novel nitric oxide-hydrogen sulfide-releasing hybrid: A new class of anti-inflammatory pharmaceuticals

Article abstract of DOI:10.1021/ml300002m

A series of new hybrids of aspirin (ASA), bearing both nitric oxide (NO) and hydrogen sulfide (H₂S)-releasing moieties were synthesized and designated as NOSH compounds (1-4). NOSH-1 (4-(3-thioxo-3H-1,2-dithiol-5-yl) phenyl 2-((4-(nitrooxy)buta

Full text of DOI:10.1021/ml300002m

Letter
pubs.acs.org/acsmedchemlett
NOSH-Aspirin: A Novel Nitric Oxide−Hydrogen Sulfide-Releasing
Hybrid: A New Class of Anti-inflammatory Pharmaceuticals
Ravinder Kodela, Mitali Chattopadhyay, and Khosrow Kashfi*
Department of Physiology and Pharmacology, Sophie Davis School of Biomedical Education, City University of New York Medical
School, New York, New York 10031, United States
S
* Supporting Information
ABSTRACT: A series of new hybrids of aspirin (ASA), bearing both nitric oxide (NO) and
hydrogen sulfide (H2S)-releasing moieties were synthesized and designated as NOSH
compounds (1−4). NOSH-1 (4-(3-thioxo-3H-1,2-dithiol-5-yl) phenyl 2-((4-(nitrooxy)-
butanoyl)oxy) benzoate); NOSH-2 (4-(nitrooxy)butyl (2-((4-(3-thioxo-3H-1,2-dithiol-5-
yl)phenoxy)carbonyl)phenyl)); NOSH-3 (4-carbamothioylphenyl 2-((4-(nitrooxy)butanoyl)-
oxy)benzoate); and NOSH-4 (4-(nitrooxy)butyl 2-(5-((R )-1,2-dithiolan-3-yl)pentanoyloxy)-
benzoate). The cell growth inhibitory properties of compounds 1−4 were evaluated in eleven
different human cancer cell lines of six different tissue origins. These cell lines are of
adenomatous (colon, pancreatic, lung, prostate), epithelial (breast), and lymphocytic
(leukemia) origin. All NOSH compounds were extremely effective in inhibiting the growth of these cell lines. NOSH-1 was
the most potent, with an IC50 of 48 3 nM in HT-29 colon cancer cells. This is the first NSAID-based compound with such
potency. This compound was also devoid of any cellular toxicity, as determined by LDH release. NOSH-1 was comparable to
aspirin in its anti-inflammatory properties, using the carrageenan rat paw edema model.
KEYWORDS: Nitric oxide, hydrogen sulfide, aspirin, anti-inflammatory, anticancer
onsteroidal anti-inflammatory drugs (NSAIDs), in
general, and aspirin, in particular, are recognized as the
either one alone. Our hypothesis has proved to be correct. Here
we describe the synthesis of four NOSH (nitric oxide-,
hydrogen sulfide-releasing) compounds that release both H2S
and NO (Figure 1). One of the compounds, NOSH-1, has
N
prototypical chemopreventive agents against many forms of
cancers.1 However, long-term use of NSAIDs may lead to
serious side effects, including gastrointestinal and renal.1 The
search for “better NSAIDs” has led to the development of
selective cyclooxygenase-2 inhibitors (Coxibs) and nitric oxide-
releasing NSAIDs (NO-NSAIDs). Several large-scale clinical
trials have shown that long-term use of coxibs is associated with
an increased risk of adverse myocardial events.2
The development of NO-NSAIDs was based on the
observation that NO has some of the same properties as
prostaglandins within the gastric mucosa. Therefore, coupling
an NO-releasing moiety to an NSAID might deliver NO to the
site of NSAID-induced damage, thereby decreasing gastric
toxicity. Animal and human studies have shown that many NO-
NSAIDs are indeed safer to the GI mucosa than the parent
NSAID.3,4
Recently, a new class of NSAIDs possessing a hydrogen
sulfide (H2S)-releasing moiety (HS-NSAIDs) have been
described in the literature.5−9 We have shown that these
compounds can be useful in controlling cancer.10−12 However,
NO-NSAIDs and HS-NSAIDs have several drawbacks, limiting
their development as pharmaceuticals. For example, HS-
NSAIDs have relatively high IC50s for cell growth inhibition.
Some NO-NSAIDs can form quinone methide intermediates,
questioning the role of NO in their biological activity.13−15
Others yet have high IC50s for cell growth inhibition.16
Therefore, we postulated that a new hybrid that incorporated
the active parts of each compound might be more potent than
Figure 1. Chemical structures of NOSH compounds.
IC50s for cell growth inhibition in the low nanomolar range and
shows strong anti-inflammatory properties.
The NOSH compounds reported here were developed by
using aspirin as a scaffold to which NO and H2S releasing
Received: January 3, 2012
Accepted: January 28, 2012
Published: January 28, 2012
© 2012 American Chemical Society
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Letter
a
Scheme 1. Synthesis of NOSH-1 and NOSH-3
a
Conditions: (i) DCC/DMAP, DCM, rt, 6 h, (ii) AgNO3, CH3CN, rt, 12 h, (iii) KMNO4, acetone, 0 °C to rt, 3 h, (iv) ADT-OH (10), DCC/
DMAP, DCM, rt, 6 h, (v) TBZ (11), DCC/DMAP, DCM, rt, 6 h.
a
Scheme 2. Synthesis of NOSH-2
a
Conditions: (ia) succinic anhydride (12), DMAP, DCM, rt, 12 h, (ib) 4-hydroxybutyl nitrate (13), DCC, rt, 6 h, (ii) KMnO4, acetone, 0 °C to rt, 3 h,
(iii) ADT-OH (10), DCC/DMAP, DCM, rt, 6 h.
moieties were coupled with one of the 1, 2 positions. We used
nitrate (-ONO2) for NO release and attached it to the aspirin
through an aliphatic spacer, while one of the following H2S-
releasing moieties, 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione
(ADT-OH), or 4-hydroxy benzothiazamide (TBZ) or lipoic
acid were directly coupled to aspirin (NOSH-1−4, Figure 1).
Salicylaldehyde was used as the starting material for NOSH-1−3,
and aspirin was used for NOSH-4.
Salicylaldehyde (5) coupled with 4-bromobutyric acid (6) in
the presence of DCC/DMAP was used to yield compound 7.
The bromo moiety in compound 7 was then substituted with
nitrate using AgNO3 to give compound 8. Then the aldehyde
group of compound 8 was oxidized to its corresponding
carboxylic group in the presence of KMnO4 to yield compound
9.17 This was then used as the precursor for preparation of
NOSH-1 and -3 using either 5-(4-hydroxyphenyl)-3H-1, 2-
dithiole-3-thione (ADT-OH, 10) or 4-hydroxythiobenzamide
(TBZ, 11), respectively (Scheme 1).
which was coupled to ADT-OH (10) in the presence of DCC/
DMAP in methylene chloride to give NOSH-2 (Scheme 2).
NOSH-4 was synthesized by using lipoic acid as H2S-
releasing donor. We used aspirin as the starting material and
coupled it with compound 13 in the presence of DCC/DMAP
to give 16.18 This then underwent deacetylation by K2CO3 in
THF/MeOH (1:1) to produce compound 17.19 This was then
coupled with (R)-lipoic acid (18) in the presence of DCC/
DMAP to produce NOSH-4 (Scheme 3).
We investigated the effects of NOSH-1−4 and ASA on the
growth properties of eleven different cancer cell lines of six
different histological subtypes. The cell lines were that of colon
(HT-29, COX-1 and COX-2 positive; HCT 15, COX null; and
SW480, COX-1 positive, low levels of endogenous COX-2),
breast (MCF7, [ER(+)]; MDA MB-231 and SKBR3,
[ER(−)]), T-cell leukemia (Jurkat), pancreas (BxPC3, both
COX-1 and COX-2 positive; MIAPaCa-2, COX-null), prostate
(LNCaP), and lung (A549). All four NOSH compounds were
extremely effective in inhibiting the growth of these cell lines
(Table 1). NOSH-1 was very potent, and its IC50 for cell
growth inhibition ranged from 48 to 280 nM. The
corresponding IC50 values for NOSH-2, -3, and -4 were 70−
120, 4300−7500, and 240−800 nM, respectively. The growth
inhibition by NOSH-1−4 versus traditional ASA was very high
in the cell lines studied. In a fold comparison study of the IC50
For preparation of compound NOSH-2, salicyladehyde (5),
succinic anhydride (12), and a catalytic amount of DMAP in
methylene chloride were treated for 24 h, at room temperature,
to prepare the succinic acid linked intermediate. To this
intermediate in situ were added hydroxybutyl nitrate (13) and
DCC to afford compound 14. This was further oxidized by
KMnO4 to its corresponding aromatic carboxylic acid (15),
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a
Scheme 3. Synthesis of NOSH-4
a
Conditions: (i) 4-hydroxybutyl nitrate (13), DCC/DMAP, DCM, rt, 6 h, (ii) K2CO3, THF/MeOH (1:1), 15 min, rt, (iii) (R)-lipoic acid (18),
DCC/DMAP, DCM, rt, 6 h.
values (ASA/NOSH-1−4), NOSH-1 was at least 100,000-fold
more potent than ASA in HT-29 colon cancer cells. The
increases in potency for NOSH-2, -3, and -4 in the same cell
line were >60,000-fold, >600-fold, and >16,000-fold, respec-
tively. In general, NOSH-1 was the most potent in all cell lines.
Cyclooxygenase (COX) represents the best-known mechanistic
target of NSAIDs. An interesting aspect of growth inhibition
also emerges with respect to COX expression in the cell lines
examined. NOSH-1−4 showed similar effects on two colon
cancer cell lines, HT-29 (expresses COX-1 and COX-2) and
HCT 15 (no COX expression),20 and on two pancreatic cancer
cell lines, BxPC-3 (expresses COXs) and MIA PaCa-2 (no
COX expression),21 suggesting a COX-independent effect.
This high degree of potency raised the question as to how
toxic this compound was to the cells. To assess this, we used
lactate dehydrogenase (LDH) release as a measure of cellular
toxicity. Cells were treated with several concentrations of
NOSH-1 for 2−24 h and compared to untreated controls.
Although the cytotoxicity caused by NOSH-1 was both dose-
and time-dependent, this was minimal (Figure 2). At 4-times its
IC50, LDH release was less than 10% at 24 h. LDH release for
shorter durations of treatment (2 h, 4 h, 6 h, and 8 h) ranged
between 0.5 and 4% at its IC50 and between 1 and 5% at 4-
times its IC50. This demonstrates a remarkable degree of safety
for a compound that is so potent.
The most common use for NSAIDs (including aspirin) is the
treatment of inflammatory conditions. Therefore, we wanted to
compare the COX-dependent anti-inflammatory activity of
ASA to that of NOSH-1. This was done by using the rat paw
edema model, as described in the Supporting Information.
After inducing inflammation in rat’s paw with carrageenan,
animals receiving vehicle showed a fast time-dependent increase
in paw volume (ΔV = 1.1 mL) after 2−3 h, which decreased
gradually every hour thereafter until the end of the experiment
(6 h) (Figure 3A). In contrast, animals receiving ASA showed a
weak inflammatory response (ΔV = 0.4 mL) at 1 h, decreasing
to about ΔV = 0.35 mL over the next 2 h and then decreasing
to about ΔV = 0.35 mL after 6 h. The anti-inflammatory effect
registered in animals treated with NOSH-1 was dose-depend-
ent. Rats treated with low dose NOSH-1 (0.21 mmol/kg)
showed a change in paw volume ΔV = 0.5 mL after 1 h which
increased to ΔV = 0.6 mL by 3 h and then came down to about
ΔV = 0.4 mL over the next 3 h. Rats treated with high dose
NOSH-1 (0.52 mmol/kg), a dose which was slightly less than
that of ASA (0.56 mmol/kg), showed a plateaued change in
paw volume of ΔV = 0.45 mL after 1−2 h, which then deceased
steadily over the next 4 h to ΔV = 0.35 mL, a change that was
comparable to that of ASA (Figure 3A).
Prostaglandins (PGE2) are the main product of cyclo-
oxygenase-mediated arachidonic acid metabolism.1 Comparison
of PGE2 content of paw exudates from control, ASA-treated,
and NOSH-1-treated animals showed a clear and significant
COX inhibition by aspirin and NOSH-1. Figure 3B shows that
aspirin (0.21 mmol/kg) caused a considerable decrease in PGE2
levels (12
group (82
3 pg/mg protein) compared with the control
2 pg/mg). Treatment with NOSH-1 reduced
PGE2 levels to 42
3 and 21
4 pg/mg at 0.21 and
0.52 mmmol/kg, respectively. We further evaluated the effect of
NOSH-1 on COX expression in paw exudates. Figure 3C
shows that COX-1 was constitutively expressed in the controls;
this was induced by carrageenan and inhibited to the same extent
by NOSH-1 regardless of the dose. On the other hand, COX-2,
which produces inflammatory PGE2, was barely detectable in the
controls, was significantly induced by carrageenan, and was dose-
dependently inhibited by NOSH-1.
We also determined the inhibitory effect of ASA and NOSH-
1 on proinflammatory cytokine tumor necrosis factor-α (TNF-
α) in plasma obtained from control and NOSH-1-treated
animals. Administration of ASA (0.56 mmol/kg) increased the
TNF-α concentration by about 20-fold (10
1 control and
200 10 pg/mL ASA); however, this rise was considerably
lower in the NOSH-1 (55 2 pg/mL at 0.21 mmol/kg and
40 3 pg/mL at 0.52 mmol/kg) treated animals (Figure 4).
The NOSH compounds were designed to release both NO
and H2S. In order to show that indeed this was the case in vivo,
blood was collected from vehicle-, ASA-, and NOSH-1-treated
animals at the end of the carrageenan-induced edema studies.
Figure 5 shows that indeed both NO and H2S were dose-
dependently significantly higher in NOSH-1-treated animals.
In the present study, we described the synthesis of four
compounds designed to release both NO and H2S. These
NOSH compounds used aspirin as a scaffold and were shown
to inhibit the growth of several cancer cell lines arising from a
variety of tissue types such as colon, breast, pancreas, lung,
prostrate, and T cell leukemia. The compounds described here
are the first to show IC50 values for cell growth inhibition that
are in the nanomolar range and yet are devoid of any cellular
toxicity. These NOSH compounds were more potent than
ASA, with enhanced potency ranging from at least 650 to
greater than 100,000-fold. Of the four NOSH compounds
evaluated here, NOSH-1 was consistently the most potent in all
cell lines tested, and in some cases this enhancement was in
excess of 150-fold over the others. Our data indicate that the
effect of these NOSH compounds may be tissue-type independent
since the NOSH-1−4 were effective against adenomatous,
epithelial, and lymphocytic cancer cell lines. Here we studied
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ACS Medicinal Chemistry Letters
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Figure 2. Toxicity profile of NOSH-1 as measured by LDH release in
HT-29 colon cancer cells.
Figure 3. Anti-inflammatory properties of NOSH-1. Rat paw edema
was induced by carrageenan injection. (A) ASA and NOSH-1
caused a significant reduction in paw volume at all time points.
Results are mean
versus vehicle treated rats at all time points. (B) ASA and NOSH-1
SEM of four rats in each group; *P < 0.05
caused a significant reduction in PGE2 levels in the paw exudate.
Results are mean
SEM for four rats in each group; *P <
0.01versus vehicle. (C) NOSH-1 inhibits induction of COX-1 and
COX-2 by carrageenan. Results show one animal is the control, four
are in carrageenan injected, and two are in NOSH-1 treated at two
different doses.
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ACS Medicinal Chemistry Letters
Letter
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Funding
Supported in part by the National Cancer Institute through a
subcontract from ThermoFisher, contract # FBS-43312-26.
Notes
The authors declare no competing financial interest.
ABBREVIATIONS
■
NSAIDs, nonsteroidal anti-inflammatory drugs; NO, nitric
oxide; H2S, hydrogen sulfide; NOSH, nitric oxide- and
hydrogen sulfide-releasing; COX, cyclooxygenase; PGE2,
prostaglandin E2; LDH, lactate dehydrogenase
Figure 4. Effect of ASA and NOSH-1 on plasma TNF-α. ASA caused a
significant rise in plasma TNF-α; however, this rise was significantly
less in the NOSH-1 treated rats. Results are mean SEM for four rats
in each group; *P < 0.01 vs vehicle, †P < 0.01 vs ASA.
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We are currently studying the molecular targets of these
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ASSOCIATED CONTENT
NSAIDs inhibit the growth of cultured human cancer cells: A general
property and evidence of a tissue type-independent effect. Biochem.
Pharmacol. 2011, DOI: 10.1016/j.bcp.2011.12.018.
■
S
* Supporting Information
Synthetic experimental details, analytical data of compounds,
and biological assay protocols. This material is available free of
charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
■
Corresponding Author
*Phone: 212-650-6641. Fax: 212-650-7692. E-mail: kashfi@
med.cuny.edu.
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