Annalisa Bruno

Mode of action of aspirin as a chemopreventive agent.

Aspirin taken for several years at doses of at least 75 mg daily reduced long-term incidence and mortality due to colorectal cancer. The finding of aspirin benefit at low-doses given once daily, used for cardioprevention, locates the antiplatelet effect of aspirin at the center of its antitumor efficacy. In fact, at low-doses, aspirin acts mainly by an irreversible inactivation of platelet cyclooxygenase (COX)-1 in the presystemic circulation, which translates into a long-lasting inhibition of platelet function. Given the short half-life of aspirin in the human circulation(approximately 20 min) and the capacity of nucleated cells to resynthesize the acetylated COX-isozyme(s), it seems unlikely that a nucleated cell could be the target of aspirin chemoprevention. These findings convincingly suggest that colorectal cancer and atherothrombosis may share a common mechanism of disease, i.e. platelet activation in response to epithelial(in tumorigenesis) and endothelial(in tumorigenesis and atherothrombosis) injury. Activated platelets may also enhance the metastatic potential of cancer cells (through a direct interaction and/or the release of soluble mediators or exosomes) at least in part by inducing the overexpression of COX-2. COX-independent mechanisms of aspirin, such as the inhibition of NF-kB signaling and Wnt/β-catenin signaling and the acetylation of extra-COX proteins, have been suggested to play a role in its chemopreventive effects. However, their relevance remains to be demonstrated in vivo at clinical doses.

Low-Dose Naproxen Interferes With the Antiplatelet Effects of Aspirin in Healthy Subjects: Recommendations to Minimize the Functional Consequences

OBJECTIVE To investigate whether low-dose naproxen sodium (220 mg twice a day) interferes with aspirins antiplatelet effect in healthy subjects. METHODS We performed a crossover, open-label study in 9 healthy volunteers. They received for 6 days 3 different treatments separated by 14 days of washout: 1) naproxen 2 hours before aspirin, 2) aspirin 2 hours before naproxen, and 3) aspirin alone. The primary end point was the assessment of serum thromboxane B(2) (TXB(2)) 24 hours after the administration of naproxen 2 hours before aspirin on day 6 of treatment. In 5 volunteers, the rate of recovery of TXB(2) generation (up to 72 hours after drug discontinuation) was assessed in serum and in platelet-rich plasma stimulated with arachidonic acid (AA) or collagen. RESULTS Twenty-four hours after the last dosing on day 6 in volunteers receiving aspirin alone or aspirin before naproxen, serum TXB(2) was almost completely inhibited (median [range] 99.1% [97.4-99.4%] and 99.1% [98.0-99.7%], respectively). Naproxen given before aspirin caused a slightly lower inhibition of serum TXB(2) (median [range] 98.0% [90.6-99.4%]) than aspirin alone (P = 0.0007) or aspirin before naproxen (P = 0.0045). All treatments produced a maximal inhibition of AA-induced platelet aggregation. At 24 hours, compared with baseline, collagen-induced platelet aggregation was still inhibited by aspirin alone (P = 0.0003), but not by aspirin given 2 hours before or after naproxen. Compared with administration of aspirin alone, the sequential administration of naproxen and aspirin caused a significant parallel upward shift of the regression lines describing the recovery of platelet TXB(2). CONCLUSION Sequential administration of 220 mg naproxen twice a day and low-dose aspirin interferes with the irreversible inhibition of platelet cyclooxygenase 1 afforded by aspirin. The interaction was smaller when giving naproxen 2 hours after aspirin. The clinical consequences of these 2 schedules of administration of aspirin with naproxen remain to be studied in randomized clinical trials.

Managing the adverse effects of nonsteroidal anti-inflammatory drugs

Conventional medical treatment for rheumatoid arthritis and osteoarthritis includes the use of NSAIDs (traditional and selective inhibitors of cyclooxygenase [COX]-2), because they provide unmistakable and significant health benefits in the treatment of pain and inflammation. However, they are associated with an increased risk of serious gastrointestinal (GI) and cardiovascular (CV) adverse events. Both beneficial and adverse effects are due to the same mechanism of action, which is inhibition of COX-dependent prostanoids. Since CV and GI risk are related to drug exposure, a reduction in the administered dose is recommended. However, this strategy will not eliminate the hazard owing to a possible contribution of individual genetic background. Further studies will be necessary to develop genetic and/or biochemical markers predictive of the CV and GI risk of NSAIDs.

Thyroid targeting of the N-ras(Gln61Lys) oncogene in transgenic mice results in follicular tumors that progress to poorly differentiated carcinomas

Ras oncogenes are frequently mutated in thyroid carcinomas. To verify the role played by N-ras in thyroid carcinogenesis, we generated transgenic mice in which a human N-ras(Gln61Lys) oncogene (Tg-N-ras) was expressed in the thyroid follicular cells. Tg-N-ras mice developed thyroid follicular neoplasms; 11% developed follicular adenomas and ∼40% developed invasive follicular carcinomas, in some cases with a mixed papillary/follicular morphology. About 25% of the Tg-N-ras carcinomas displayed large, poorly differentiated areas, featuring vascular invasion and forming lung, bone or liver distant metastases. N-ras(Gln61Lys) expression in cultured PC Cl 3 thyrocytes induced thyroid-stimulating hormone-independent proliferation and genomic instability with micronuclei formation and centrosome amplification. These findings support the notion that mutated ras oncogenes could be able to drive the formation of thyroid tumors that can progress to poorly differentiated, metastatic carcinomas.

Synthesis, Pharmacological Characterization, and Docking Analysis of a Novel Family of Diarylisoxazoles as Highly Selective Cyclooxygenase-1 (COX-1) Inhibitors

3-(5-Chlorofuran-2-yl)-5-methyl-4-phenylisoxazole (P6), a known selective cyclooxygenase-1 (COX-1) inhibitor, was used to design a new series of 3,4-diarylisoxazoles in order to improve its biochemical COX-1 selectivity and antiplatelet efficacy. Structure-activity relationships were studied using human whole blood assays for COX-1 and COX-2 inhibition in vitro, and results showed that the simultaneous presence of 5-methyl (or -CF3), 4-phenyl, and 5-chloro(-bromo or -methyl)furan-2-yl groups on the isoxazole core was essential for their selectivity toward COX-1. 3g, 3s, 3d were potent and selective COX-1 inhibitors that affected platelet aggregation in vitro through the inhibition of COX-1-dependent thromboxane (TX) A2. Moreover, we characterized their kinetics of COX-1 inhibition. 3g, 3s, and 3d were more potent inhibitors of platelet COX-1 and aggregation than P6 (named 6) for their tighter binding to the enzyme. The pharmacological results were supported by docking simulations. The oral administration of 3d to mice translated into preferential inhibition of platelet-derived TXA2 over protective vascular-derived prostacyclin (PGI2).

Aspirin prevents colorectal cancer metastasis in mice by splitting the crosstalk between platelets and tumor cells

We investigated whether platelets prime colon cancer cells for metastasis and whether pharmacological inhibition of platelet function may prevent it. Coculturing HT29 human colon carcinoma cells with human platelets led to the induction of mesenchymal-like cancer cells characterized by downregulation of E-cadherin and upregulation of Twist1, enhanced cell mobility and a proaggregatory action on platelets. These changes were prevented by different antiplatelet agents, aspirin[an inhibitor of cyclooxygenase(COX)-1], DG-041[an antagonist of prostaglandin(PG)E2 EP3 receptor] and ticagrelor (a P2Y12 receptor antagonist). The injection of HT29 cells, exposed to platelets in vitro, into the tail vein of humanized immunodeficient mice led to higher incidence of lung metastasis compared to the injection of untreated HT29 cells. This effect was associated with enhanced systemic biosynthesis of thromboxane(TX)A2 and PGE2 in vivo. Platelet COX-1 inhibition by aspirin administration to mice prevented the increased rate of metastasis as well as the enhanced production of TXA2 and PGE2 induced by the in vitro priming of HT29 cells by platelets. In conclusion, targeting platelet COX-1 with low-dose aspirin exerts an antimetastatic action by averting the stem cell mimicry of cancer cells associated with enhanced proaggregatory effects induced by platelet-tumor cell interactions. These effects may be shared by other antiplatelet drugs.

Effects of AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide], a novel inhibitor of human microsomal prostaglandin E synthase-1, on prostanoid biosynthesis in human monocytes in vitro.

Inhibitors of microsomal prostaglandin (PG) E synthase-1 (mPGES-1) are being developed for the relief of pain. Redirection of the PGH(2) substrate to other PG synthases, found both in vitro and in vivo, in mPGES-1 knockout mice, may influence their efficacy and safety. We characterized the contribution of mPGES-1 to PGH(2) metabolism in lipopolysaccharide (LPS)-stimulated isolated human monocytes and whole blood by studying the synthesis of prostanoids [PGE(2), thromboxane (TX)B(2), PGF(2alpha) and 6-keto-PGF(1alpha)] and expression of cyclooxygenase (COX)-isozymes and down-stream synthases in the presence of pharmacological inhibition by the novel mPGES-1 inhibitor AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide]. AF3442 caused a concentration-dependent inhibition of PGE(2) in human recombinant mPGES-1 with an IC(50) of 0.06microM. In LPS-stimulated monocytes, AF3442 caused a concentration-dependent reduction of PGE(2) biosynthesis with an IC(50) of 0.41microM. At 1microM, AF3442 caused maximal selective inhibitory effect of PGE(2) biosynthesis by 61+/-3.3% (mean+/-SEM, P<0.01 versus DMSO vehicle) without significantly affecting other prostanoids (i.e. TXB(2), PGF(2alpha) and 6-keto-PGF(1alpha)). In LPS-stimulated whole blood, AF3442 inhibited in a concentration-dependent fashion inducible PGE(2) biosynthesis with an IC(50) of 29microM. A statistically significant inhibition of mPGES-1 activity was detected at 10 and 100microM (38+/-14%, P<0.05, and 69+/-5%, P<0.01, respectively). Up to 100microM, the other prostanoids were not significantly affected. In conclusion, AF3442 is a selective mPGES-1 inhibitor which reduced monocyte PGE(2) generation also in the presence of plasma proteins. Pharmacological inhibition of mPGES-1 did not translate into redirection of PGH(2) metabolism towards other terminal PG synthases in monocytes. The functional relevance of this observation deserves to be investigated in vivo.

Variability in the Response to Non‐Steroidal Anti‐Inflammatory Drugs: Mechanisms and Perspectives

Non-steroidal anti-inflammatory drugs (NSAIDs) are a chemically heterogeneous group of compounds that provide unmistakable and significant health benefits in the treatment of pain and inflammation. They include traditional NSAIDs (tNSAIDs), which act by inhibiting both cyclooxygenase (COX)-1 and COX-2 and selective COX-2 inhibitors (coxibs). The development of biomarkers predictive of the impact of NSAIDs on COX-1 and COX-2 activities in vitro, ex vivo and in vivo has been essential to read out the clinical consequences of selective and non-selective inhibition of COX isozymes in human beings. The analgesic and anti-inflammatory effects of NSAIDs are COX-2-dependent effects, unrelated to COX-2 selectivity. The intensity and duration of these effects are influenced by dose and half-life of the NSAID. However, the inhibition of COX-1 in cells of the gastrointestinal (GI) system and COX-2 in vascular cells translates into increased risk of serious GI adverse events and atherothrombosis and hypertension, respectively. The COX-2 selectivity of NSAIDs can predict, at least in part, the GI toxicity. In contrast, the CV effects are largely COX-2-dependent effects, unrelated to COX-2 selectivity but are dose dependent. The reduction in the dose is recommended and presumably will limit the number of patients exposed to a CV or a GI hazard by NSAIDs and coxibs. It will not, however, eliminate the risk on an individual level because there is a marked variability in how different people react to these drugs, based on their genetic background. The challenge of the next future will be to develop biomarkers useful to identify the individuals who react abnormally to COX inhibition.

Effects of celecoxib on prostanoid biosynthesis and circulating angiogenesis proteins in familial adenomatous polyposis

Vascular cyclooxygenase (COX)-2-dependent prostacyclin (PGI2) may affect angiogenesis by preventing endothelial activation and platelet release of angiogenic factors present in platelet α-granules. Thus, a profound inhibition of COX-2-dependent PGI2 might be associated with changes in circulating markers of angiogenesis. We aimed to address this issue by performing a clinical study with celecoxib in familial adenomatous polyposis (FAP). In nine patients with FAP and healthy controls, pair-matched for gender and age, we compared systemic biosynthesis of PGI2, thromboxane (TX) A2, and prostaglandin (PG) E2, assessing their urinary enzymatic metabolites, 2,3-dinor-6-keto PGF1α (PGI-M), 11-dehydro-TXB2 (TX-M), and 11-α-hydroxy-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M), respectively. The impact of celecoxib (400 mg b.i.d. for 7 days) on prostanoid biosynthesis and 14 circulating biomarkers of angiogenesis was evaluated in FAP. Intestinal tumorigenesis was associated with enhanced urinary TX-M levels, but unaffected by celecoxib, suggesting the involvement of a COX-1-dependent pathway, presumably from platelets. This was supported by the finding that in cocultures of a human colon adenocarcinoma cell line (HT-29) and platelets enhanced TXA2 generation was almost completely inhibited by pretreatment of platelets with aspirin, a preferential inhibitor of COX-1. In FAP, celecoxib profoundly suppressed PGE2 and PGI2 biosynthesis that was associated with a significant increase in circulating levels of most proangiogenesis proteins but also the antiangiogenic tissue inhibitor of metalloproteinase 2. Urinary PGI-M, but not PGE-M, was negatively correlated with circulating levels of fibroblast growth factor 2 and angiogenin. In conclusion, inhibition of tumor COX-2-dependent PGE2 by celecoxib may reduce tumor progression. However, the coincident depression of vascular PGI2, in a context of enhanced TXA2 biosynthesis, may modulate the attendant angiogenesis, contributing to variability in the chemopreventive efficacy of COX-2 inhibitors such as celecoxib.

Novel analgesic/anti-inflammatory agents: diarylpyrrole acetic esters endowed with nitric oxide releasing properties.

The design of compounds that are able to inhibit cyclooxygenase (COX) and to release nitric oxide (NO) should give rise to drugs endowed with an overall safer profile for the gastrointestinal and cardiovascular systems. Herein we report a new class of pyrrole-derived nitrooxy esters (11a-j), cyclooxygenase-2 (COX-2) selective inhibitors endowed with NO releasing properties, with the goal of generating new molecules able to both strongly inhibit this isoform and reduce the related adverse side effects. Taking into account the metabolic conversion of nitrooxy esters into corresponding alcohols, we also studied derivatives 12a-j. All compounds proved to be very potent and selective COX-2 inhibitors; nitrooxy derivatives displayed interesting ex vivo NO-dependent vasorelaxing properties. Compounds 11c, 11d, 12c, and 12d were selected for further in vivo studies that highlited good anti-inflammatory and antinociceptive activities. Finally, two selected compounds (11c and 12c) tested in human whole blood (HWB) assay proved to be preferential inhibitors of COX-2.