NOSH-aspirin (NBS-1120), a novel nitric oxide- and hydrogen sulfide-releasing hybrid has enhanced chemo-preventive properties compared to aspirin, is gastrointestinal safe with all the classic therapeutic indications

Abstract

Aspirin is chemopreventive; however, side effects preclude its long-term use. NOSH-aspirin (NBS-1120), a novel hybrid that releases nitric oxide and hydrogen sulfide, was designed to be a safer alternative. Here we compare the gastrointestinal safety, anti-inflammatory, analgesic, anti-pyretic, anti-platelet, and chemopreventive properties of aspirin and NBS-1120 administered orally to rats at equimolar doses. Gastrointestinal safety: 6h post-administration, the number and size of hemorrhagic lesions in stomachs were counted; tissue samples were frozen for PGE2, SOD, and MDA determination. Anti-inflammatory: 1h after drug administration, the volume of carrageenan-induced rat paw edemas was measured for 5h. Anti-pyretic: fever was induced by LPS (ip) an hour before administration of the test drugs, core body temperature was measured hourly for 5h. Analgesic: time-dependent analgesic effects were evaluated by carrageenan-induced hyperalgesia. Antiplatelet: anti-aggregatory effects were studied on collagen-induced platelet aggregation of human platelet-rich plasma. Chemoprevention: nude mice were gavaged daily for 25 days with vehicle, aspirin or NBS-1120. After one week, each mouse was inoculated subcutaneously in the right flank with HT-29 human colon cancer cells. Both agents reduced PGE2 levels in stomach tissue; however, NBS-1120 did not cause any stomach ulcers, whereas aspirin caused significant bleeding. Lipid peroxidation induced by aspirin was higher than that exerted by NBS-1120. SOD activity was significantly inhibited by aspirin but increased by NBS-1120. Both agents showed similar anti-inflammatory, analgesic, anti-pyretic, and anti-platelet activities. Aspirin increased plasma TNFα more than NBS-1120-treated animals. NBS-1120 was better than aspirin as a chemopreventive agent; it dose-dependently inhibited tumor growth and tumor mass.

Keywords: Aspirin; Chemopreventive; GI-sparing; Hydrogen sulfide; Nitric oxide.

Figure 1

Structural components of NOSH-aspirin. The parent compound aspirin is shown in the shaded box. The parts of the molecule that releases NO and H2S are shown in the dotted ellipses.

Figure 2

NOSH-aspirin does not cause gastric damage. Aspirin and NOSH-aspirin were administered orally at equimolar doses (1 mmol/kg) and effects on the stomach were evaluated 6 hrs post-administration as indicated in Section 2.2. Panel A, shows the stomach of a vehicle-treated rat; Panel B, stomach of an aspirin-treated rat showing ulceration and bleeding; Panel C, stomach of a NOSH-aspirin-treated rat which is devoid of ulcers. Panel D, gastric damage due to aspirin, UI = 48 ± 4 mm (†P < 0.01 compared to vehicle), whereas NOSH-aspirin was gastric damage-sparing, UI = 2 ± 0.5 mm (*P < 0.01 compared to aspirin).

Figure 3

Effects of aspirin and NOSH-aspirin on gastric PGE2 level, lipid peroxidation (MDA) and superoxide dismutase (SOD). Three groups of rats were treated with vehicle, aspirin, and NOSH-aspirin for 6 hrs and their stomachs removed and processed as described in Sections 2.2–2.5. Aspirin, and NOSH-aspirin caused a significant reduction in gastric mucosal PGE2 levels (panel A). Results are mean ± SEM of 5 rats in each group, *P < 0.05 vs vehicle group, §P < 0.05 vs NOSH-aspirin group. Aspirin caused an almost 8-fold increase in MDA levels, for NOSH-aspirin-treated rats, MDA levels were about 2-fold higher (panel B). Results are mean ± SEM for 5 rats in each group, †P < 0.01 vs vehicle group, §P < 0.01 vs aspirin group. Aspirin caused a significant reduction in SOD activity, whereas NOSH-aspirin caused an increase (panel C). Results are mean ± SEM of 5 rats, *P < 0.05 vs vehicle group, **P < 0.01 vs aspirin group.

Figure 4

Anti-inflammatory properties of aspirin and NOSH-aspirin. Rat paw edema was induced by carrageenan injection as described in Section 2.8. Aspirin and NOSH-aspirin caused a significant reduction in paw volume at all time points (panel A). Results are mean ± SEM of 5 rats in each group, *P < 0.05 vs vehicle treated rats at all time points. Aspirin and NOSH-aspirin also caused a significant reduction in PGE2 levels in the paw exudate (panel B). Results are mean ± SEM for 5 rats in each group, †P< 0.01 vs vehicle, *P <0.05 vs NOSH-aspirin.

Figure 5

Effect of aspirin and NOSH-aspirin on plasma TNF-α. Rats were treated with equimolar amounts (1 mmol/kg) of aspirin and NOSH-aspirin and plasma TNF-α was measured as described in Section 2.6. Aspirin caused a significant rise in plasma TNF-α, however, this rise was significantly less in the NOSH-aspirin-treated rats. Results are mean ± SEM for 5 rats in each group, *P < 0.001 vs vehicle, §P < 0.01 vs aspirin.

Figure 6

Aspirin and NOSH-aspirin reduce LPS-induced fever, raise the threshold for hyperalgesia, and show anti-platelet activity. Panel A: LPS (50 μg/kg, ip) was administered to the rats one hour before administration aspirin and NOSH-aspirin as described in Section 2.7. Core body temperature was recorded at 30 min and thereafter hourly for 5 h. Results are mean ± SEM for 5 rats in each group, *P < 0.01 vs vehicle for both aspirin and NOSH-aspirin from 1–5 h. Panel B: Mechanical pain threshold was increased in a time-dependent manner by aspirin and NOSH-aspirin as detailed in Section 2.9. Results are mean ± SEM for 5 rats in each group. *P < 0.05 vs vehicle for aspirin and NOSH-aspirin 2–5 h. Panel C: Aspirin and NOSH-aspirin were equally effective in inhibiting human platelet aggregation, protocol as described in Section 2.10. Results are mean ± range for two individuals.

Figure 7

NOSH-aspirin prevents tumor xenograft growth. Panel A: Study protocol. Athymic nude male mice were treated for 7 days via gavage with vehicle (Panel B), or NOSH-aspirin (25, 50, 100 mg/kg, Panels C–E), or aspirin (50 mg/kg, Panel F) and then injected subcutaneously with HT-29 cells for the development of subcutaneous tumors as described in Section 2.11. Daily administration of the test agents continued to the end of the experiment. Tumor sizes for untreated and treated mice are shown in Panel G.

Figure 8

NOSH-aspirin and aspirin reduce tumor growth and tumor mass. Animals were treated as depicted in Fig 7. Average tumor volume as function of time and tumor mass at sacrifice are shown in Panels A and B, respectively. NOSH-aspirin dose-dependently and aspirin at 50 mg/kg significantly reduced tumor growth from day 18 post inoculation to sacrifice, *P < 0.01. Tumor mass was also significantly and dose-dependently reduced by NOSH-aspirin treatment, *P < 0.01 and aspirin at 50 mg/kg (†P < 0.05).