Platelets and extracellular vesicles in disease promotion via cellular cross-talk and eicosanoid biosynthesis.

New insights have been gained on the role of platelets beyond thrombosis. Platelets can accumulate in damaged and inflamed tissues, acting as a sentinel to detect and repair tissue damage. However, by releasing several soluble factors, including thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid, and extracellular vesicles (EVs), platelets can activate vascular cells, stromal, such as fibroblasts, immune cells, and cancer cells, leading to atherosclerosis, vascular restenosis, tissue fibrosis, and tumor metastasis. Platelet-derived extracellular vesicles (PEVs) are released when platelets are activated and can transfer their cargo to other cell types, thus contributing to the development of diseases. Inhibitors of the internalization of PEVs can potentially represent novel therapeutic tools. Both platelets and PEVs contain a significant number of different types of molecules, and their omics assessment and integration with clinical data using computational approaches have the potential to detect early disease development and monitor drug treatments.

The specific deletion of cyclooxygenase-1 in megakaryocytes/platelets reduces intestinal polyposis in ApcMin/+ mice.

Clinical and experimental evidence sustain the role of cyclooxygenase (COX)-1 in intestinal tumorigenesis. However, the cell type expressing the enzyme involved and molecular mechanism(s) have not been clarified yet. We aimed to elucidate the role of platelet COX-1 (the target of low-dose aspirin in humans) in intestinal tumorigenesis of ApcMin/+ mice, considered a clinically relevant model. To realize this objective, we generated an ApcMin/+ mouse with a specific deletion of Ptgs1(COX-1 gene name) in megakaryocytes/platelets (ApcMin/+;pPtgs1-/-mice) characterized by profound inhibition of thromboxane(TX)A2 biosynthesis ex vivo (serum TXB2; by 99%) and in vivo [urinary 2,3-dinor-TXB2(TXM), by 79%]. ApcMin/+ mice with the deletion of platelet COX-1 showed a significantly reduced number (67%) and size (32%) of tumors in the small intestine. The intestinal adenomas of these mice had decreased proliferative index associated with reduced COX-2 expression and systemic prostaglandin(PG)E2 biosynthesis (urinary PGEM) vs. ApcMin/+mice. Extravasated platelets were detected in the intestine of ApcMin/+mice. Thus, we explored their contribution to COX-2 induction in fibroblasts, considered the primary polyp cell type expressing the protein. In the coculture of human platelets and myofibroblasts, platelet-derived TXA2 was involved in the induction of COX-2-dependent PGE2 in myofibroblasts since it was prevented by the selective inhibition of platelet COX-1 by aspirin or by a specific antagonist of TXA2 receptors. In conclusion, our results support the platelet hypothesis of intestinal tumorigenesis and provide experimental evidence that selective inhibition of platelet COX-1 can mitigate early events of intestinal tumorigenesis by restraining COX-2 induction.

Platelets induce free and phospholipid-esterified 12-hydroxyeicosatetraenoic acid generation in colon cancer cells by delivering 12-lipoxygenase.

Platelets promote tumor metastasis by inducing promalignant phenotypes in cancer cells and directly contributing to cancer-related thrombotic complications. Platelet-derived extracellular vesicles (EVs) can promote epithelial-mesenchymal transition (EMT) in cancer cells, which confers high-grade malignancy. 12S-hydroxyeicosatetraenoic acid (12-HETE) generated by platelet-type 12-lipoxygenase (12-LOX) is considered a key modulator of cancer metastasis through unknown mechanisms. In platelets, 12-HETE can be esterified into plasma membrane phospholipids (PLs), which drive thrombosis. Using cocultures of human platelets and human colon adenocarcinoma cells (line HT29) and LC-MS/MS, we investigated the impact of platelets on cancer cell biosynthesis of 12S-HETE and its esterification into PLs and whether platelet ability to transfer its molecular cargo might play a role. To this aim, we performed coculture experiments with CFSE[5-(and-6)-carboxyfluorescein diacetate, succinimidyl ester]-loaded platelets. HT29 cells did not generate 12S-HETE or express 12-LOX. However, they acquired the capacity to produce 12S-HETE mainly esterified in plasmalogen phospholipid forms following the uptake of platelet-derived medium-sized EVs (mEVs) expressing 12-LOX. 12-LOX was detected in plasma mEV of patients with adenomas/adenocarcinomas, implying their potential to deliver the protein to cancer cells in vivo. In cancer cells exposed to platelets, endogenous but not exogenous 12S-HETE contributed to changes in EMT gene expression, mitigated by three structurally unrelated 12-LOX inhibitors. In conclusion, we showed that platelets induce the generation of primarily esterified 12-HETE in colon cancer cells following mEV-mediated delivery of 12-LOX. The modification of cancer cell phospholipids by 12-HETE may functionally impact cancer cell biology and represent a novel target for anticancer agent development.

Low-dose Aspirin prevents hypertension and cardiac fibrosis when thromboxane A2 is unrestrained.

Enhanced platelet activation has been reported in patients with essential hypertension and heart failure. The possible contribution of platelet-derived thromboxane (TX)A2 in their pathophysiology remains unclear. We investigated the systemic TXA2 biosynthesis in vivo and gene expression of its receptor TP in 22 essential hypertension patients and a mouse model of salt-sensitive hypertension. The contribution of platelet TXA2 biosynthesis on enhanced blood pressure (BP) and overload-induced cardiac fibrosis was explored in mice by treating with low-dose Aspirin, resulting in selective inhibition of platelet cyclooxygenase (COX)-1-dependent TXA2 generation. In essential hypertensive patients, systemic biosynthesis of TXA2 [assessed by measuring its urinary metabolites (TXM) reflecting predominant platelet source] was enhanced together with higher gene expression of circulating leukocyte TP and TGF-ß, vs. normotensive controls. Similarly, in hypertensive mice with prostacyclin (PGI2) receptor (IP) deletion (IPKO) fed with a high-salt diet, enhanced urinary TXM, and left ventricular TP overexpression were detected vs. normotensive wildtype (WT) mice. Increased cardiac collagen deposition and profibrotic gene expression (including TGF-ß) was found. Low-dose Aspirin administration caused a selective inhibition of platelet TXA2 biosynthesis and mitigated enhanced blood pressure, cardiac fibrosis, and left ventricular profibrotic gene expression in IPKO but not WT mice. Moreover, the number of myofibroblasts and extravasated platelets in the heart was reduced. In cocultures of human platelets and myofibroblasts, platelet TXA2 induced profibrotic gene expression, including TGF-ß1. In conclusion, our results support tailoring low-dose Aspirin treatment in hypertensive patients with unconstrained TXA2/TP pathway to reduce blood pressure and prevent early cardiac fibrosis.

miR-574-5p as RNA decoy for CUGBP1 stimulates human lung tumor growth by mPGES-1 induction.

MicroRNAs (miRs) are important posttranscriptional regulators of gene expression. Besides their well-characterized inhibitory effects on mRNA stability and translation, miRs can also activate gene expression. In this study, we identified a novel noncanonical function of miR-574-5p. We found that miR-574-5p acts as an RNA decoy to CUG RNA-binding protein 1 (CUGBP1) and antagonizes its function. MiR-574-5p induces microsomal prostaglandin E synthase-1 (mPGES-1) expression by preventing CUGBP1 binding to its 3'UTR, leading to an enhanced alternative splicing and generation of an mPGES-1 3'UTR isoform, increased mPGES-1 protein expression, PGE2 formation, and tumor growth in vivo. miR-574-5p-induced tumor growth in mice could be completely inhibited with the mPGES-1 inhibitor CIII. Moreover, miR-574-5p is induced by IL-1ß and is strongly overexpressed in human nonsmall cell lung cancer where high mPGES-1 expression correlates with a low survival rate. The discovered function of miR-574-5p as a CUGBP1 decoy opens up new therapeutic opportunities. It might serve as a stratification marker to select lung tumor patients who respond to the pharmacological inhibition of PGE2 formation.-Saul, M. J., Baumann, I., Bruno, A., Emmerich, A. C., Wellstein, J., Ottinger, S. M., Contursi, A., Dovizio, M., Donnini, S., Tacconelli, S., Raouf, J., Idborg, H., Stein, S., Korotkova, M., Savai, R., Terzuoli, E., Sala, G., Seeger, W., Jakobsson, P.-J., Patrignani, P., Suess, B., Steinhilber, D. miR-574-5p as RNA decoy for CUGBP1 stimulates human lung tumor growth by mPGES-1 induction.

Multifaceted Functions of Platelets in Cancer: From Tumorigenesis to Liquid Biopsy Tool and Drug Delivery System.

Platelets contribute to several types of cancer through plenty of mechanisms. Upon activation, platelets release many molecules, including growth and angiogenic factors, lipids, and extracellular vesicles, and activate numerous cell types, including vascular and immune cells, fibroblasts, and cancer cells. Hence, platelets are a crucial component of cell-cell communication. In particular, their interaction with cancer cells can enhance their malignancy and facilitate the invasion and colonization of distant organs. These findings suggest the use of antiplatelet agents to restrain cancer development and progression. Another peculiarity of platelets is their capability to uptake proteins and transcripts from the circulation. Thus, cancer-patient platelets show specific proteomic and transcriptomic expression patterns, a phenomenon called tumor-educated platelets (TEP). The transcriptomic/proteomic profile of platelets can provide information for the early detection of cancer and disease monitoring. Platelet ability to interact with tumor cells and transfer their molecular cargo has been exploited to design platelet-mediated drug delivery systems to enhance the efficacy and reduce toxicity often associated with traditional chemotherapy. Platelets are extraordinary cells with many functions whose exploitation will improve cancer diagnosis and treatment.

Platelet-Specific Deletion of Cyclooxygenase-1 Ameliorates Dextran Sulfate Sodium-Induced Colitis in Mice.

Inflammatory bowel disease (IBD) is associated with an increased risk for thromboembolism, platelet activation, and abnormalities in platelet number and size. In colitis, platelets can extravasate into the colonic interstitium. We generated a mouse with a specific deletion of cyclooxygenase (COX)-1 in megakaryocytes/platelets [(COX-1 conditional knockout (cKO)] to clarify the role of platelet activation in the development of inflammation and fibrosis in dextran sodium sulfate (DSS)-induced colitis. The disease activity index was assessed, and colonic specimens were evaluated for histologic features of epithelial barrier damage, inflammation, and fibrosis. Cocultures of platelets and myofibroblasts were performed. We found that the specific deletion of COX-1 in platelets, which recapitulated the human pharmacodynamics of low-dose aspirin, that is, suppression of platelet thromboxane (TX)A2 production associated with substantial sparing of the systemic production of prostacyclin, resulted in milder symptoms of colitis, in the acute phase, and almost complete recovery from the disease after DSS withdrawal. Reduced colonic accumulation of macrophages and myofibroblasts and collagen deposition was found. Platelet-derived TXA2 enhanced the ability of myofibroblasts to proliferate and migrate in vitro, and these effects were prevented by platelet COX-1 inhibition or antagonism of the TXA2 receptor. Our findings allow a significant advance in the knowledge of the role of platelet-derived TXA2 in the development of colitis and fibrosis in response to intestinal damage and provide the rationale to investigate the potential efficacy of the antiplatelet agent low-dose aspirin in limiting the inflammatory response and fibrosis associated with IBD. SIGNIFICANCE STATEMENT: Inflammatory bowel disease (IBD) is characterized by the development of a chronic inflammatory response, which can lead to intestinal fibrosis for which currently there is no medical treatment. Through the generation of a mouse with specific deletion of cyclooxygenase-1 in megakaryocytes/platelets, which recapitulates the human pharmacodynamics of low-dose aspirin, we demonstrate the important role of platelet-derived thromboxane A2 in the development of experimental colitis and fibrosis, thus providing the rationale to investigate the potential efficacy of low-dose aspirin in limiting the inflammation and tissue damage associated with IBD.

Gut microbiota, host gene expression, and aging.

Novel concepts of disease susceptibility and development suggest an important role of gastrointestinal microbiota and microbial pathogens. They can contribute to physiological systems and disease processes, even outside of the gastrointestinal tract. There is increasing evidence that genetics of the host influence and interact with gut microbiota. Moreover, aging-associated oxidative stress may cause morphologic alterations of bacterial cells, thus influencing the aggressive potential and virulence markers of an anaerobic bacterium and finally the type of interaction with the host. At the same time, microbiota may influence host gene expression and it is becoming apparent that it may occur through the regulation of microRNAs. They are short single-stranded noncoding RNAs that regulate posttranscriptional gene expression by affecting mRNA stability and/or translational repression of their target mRNAs. The introduction of -omics approaches (such as metagenomics, metaproteomics, and metatranscriptomics) in microbiota research will certainly advance our knowledge of this area. This will lead to greatly deepen our understanding of the molecular targets in the homeostatic interaction between the gut microbiota and the host and, thereby, promises to reveal new ways to treat diseases and maintain health.

Optimizing aspirin dose for colorectal cancer patients through deep phenotyping using novel biomarkers of drug action.

Background: Low-dose aspirin's mechanism of action for preventing colorectal cancer (CRC) is still debated, and the optimal dose remains uncertain. We aimed to optimize the aspirin dose for cancer prevention in CRC patients through deep phenotyping using innovative biomarkers for aspirin's action. Methods: We conducted a Phase II, open-label clinical trial in 34 CRC patients of both sexes randomized to receive enteric-coated aspirin 100 mg/d, 100 mg/BID, or 300 mg/d for 3 ± 1 weeks. Biomarkers were evaluated in blood, urine, and colorectal biopsies at baseline and after dosing with aspirin. Novel biomarkers of aspirin action were assessed in platelets and colorectal tissues using liquid chromatography-mass spectrometry to quantify the extent of cyclooxygenase (COX)-1 and COX-2 acetylation at Serine 529 and Serine 516, respectively. Results: All aspirin doses caused comparable % acetylation of platelet COX-1 at Serine 529 associated with similar profound inhibition of platelet-dependent thromboxane (TX)A2 generation ex vivo (serum TXB2) and in vivo (urinary TXM). TXB2 was significantly reduced in CRC tissue by aspirin 300 mg/d and 100 mg/BID, associated with comparable % acetylation of COX-1. Differently, 100 mg/day showed a lower % acetylation of COX-1 in CRC tissue and no significant reduction of TXB2. Prostaglandin (PG)E2 biosynthesis in colorectal tumors and in vivo (urinary PGEM) remained unaffected by any dose of aspirin associated with the variable and low extent of COX-2 acetylation at Serine 516 in tumor tissue. Increased expression of tumor-promoting genes like VIM (vimentin) and TWIST1 (Twist Family BHLH Transcription Factor 1) vs. baseline was detected with 100 mg/d of aspirin but not with the other two higher doses. Conclusion: In CRC patients, aspirin 300 mg/d or 100 mg/BID had comparable antiplatelet effects to aspirin 100 mg/d, indicating similar inhibition of the platelet's contribution to cancer. However, aspirin 300 mg/d and 100 mg/BID can have additional anticancer effects by inhibiting cancerous tissue's TXA2 biosynthesis associated with a restraining impact on tumor-promoting gene expression. EUDRACT number: 2018-002101-65. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT03957902.

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/ß-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.

Coxibs: pharmacology, toxicity and efficacy in cancer clinical trials.

This chapter briefly summarizes the current knowledge about the role of nonsteroidal anti-inflammatory drugs (NSAIDs), specially focusing on those selective for cyclooxygenase (COX)-2 (coxibs), on colorectal cancer (CRC) onset, and progression. Both epidemiological and experimental studies have reported that these drugs reduce the risk of developing colonic tumors. However, the promising use of coxibs in chemoprevention was halted abruptly due to the detection on enhanced cardiovascular (CV) risks. Thus, we discuss the clinical data and plausible mechanisms of CV hazards associated with traditional NSAIDs and coxibs. The extent of inhibition of COX-2-dependent prostacyclin, an important vasoprotective and anti-thrombotic pathway, in the absence of a complete suppression of COX-1-dependent platelet function, at common doses of NSAIDs, might play a role in CV toxicity. Coxibs might still be reserved for younger patients with familial adenomatous polyposis (FAP). However, it should be taken into consideration that recent findings of enhanced thromboxane (TX)A(2) biosynthesis in colon tumorigenesis, detected in humans. In this context, the use of low-dose aspirin (which mainly acts by inhibiting platelet COX-1-dependent TXA(2)) may have a place for chemoprevention of CRCs (see also Chap. 3 ). The possible use of coxibs to prevent CRC will depend mainly on research progresses in biomarkers able to identify the patients uniquely susceptible to developing thrombotic events by inhibition of COX-2.

Cyclooxygenases and platelet functions.

Cyclooxygenase (COX) isozymes, i.e., COX-1 and COX-2, are encoded by separate genes and are involved in the generation of the same products, prostaglandin (PG)G2 and PGH2 from arachidonic acid (AA) by the COX and peroxidase activities of the enzymes, respectively. PGH2 is then transformed into prostanoids in a tissue-dependent fashion due to the different expression of downstream synthases. Platelets present almost exclusively COX-1, which generates large amounts of thromboxane (TX)A2, a proaggregatory and vasoconstrictor mediator. This prostanoid plays a central role in atherothrombosis, as shown by the benefit of the antiplatelet agent low-dose aspirin, a preferential inhibitor of platelet COX-1. Recent findings have shown the relevant role played by platelets and TXA2 in developing chronic inflammation associated with several diseases, including tissue fibrosis and cancer. COX-2 is induced in response to inflammatory and mitogenic stimuli to generate PGE2 and PGI2 (prostacyclin), in inflammatory cells. However, PGI2 is constitutively expressed in vascular cells in vivo and plays a crucial role in protecting the cardiovascular systems due to its antiplatelet and vasodilator effects. Here, platelets' role in regulating COX-2 expression in cells of the inflammatory microenvironment is described. Thus, the selective inhibition of platelet COX-1-dependent TXA2 by low-dose aspirin prevents COX-2 induction in stromal cells leading to antifibrotic and antitumor effects. The biosynthesis and functions of other prostanoids, such as PGD2, and isoprostanes, are reported. In addition to aspirin, which inhibits platelet COX-1 activity, possible strategies to affect platelet functions by influencing platelet prostanoid receptors or synthases are discussed.

Tumor-Educated Platelet Extracellular Vesicles: Proteomic Profiling and Crosstalk with Colorectal Cancer Cells.

BACKGROUND: Platelet-cancer cell interactions modulate tumor metastasis and thrombosis in cancer. Platelet-derived extracellular vesicles (EVs) can contribute to these outcomes. METHODS: We characterized the medium-sized EVs (mEVs) released by thrombin-stimulated platelets of colorectal cancer (CRC) patients and healthy subjects (HS) on the capacity to induce epithelial-mesenchymal transition (EMT)-related genes and cyclooxygenase (COX)-2(PTGS2), and thromboxane (TX)B2 production in cocultures with four colorectal cancer cell lines. Platelet-derived mEVs were assessed for their size distribution and proteomics signature. RESULTS: The mEV population released from thrombin-activated platelets of CRC patients had a different size distribution vs. HS. Platelet-derived mEVs from CRC patients, but not from HS, upregulated EMT marker genes, such as TWIST1 and VIM, and downregulated CDH1. PTGS2 was also upregulated. In cocultures of platelet-derived mEVs with cancer cells, TXB2 generation was enhanced. The proteomics profile of mEVs released from activated platelets of CRC patients revealed that 119 proteins were downregulated and 89 upregulated vs. HS. CONCLUSIONS: We show that mEVs released from thrombin-activated platelets of CRC patients have distinct features (size distribution and proteomics cargo) vs. HS and promote prometastatic and prothrombotic phenotypes in cancer cells. The analysis of platelet-derived mEVs from CRC patients could provide valuable information for developing an appropriate treatment plan.

Biomarkers of Response to Low-Dose Aspirin in Familial Adenomatous Polyposis Patients.

BACKGROUND: The results of Aspirin prevention of colorectal adenomas in patients with familial adenomatous polyposis (FAP) are controversial. METHODS: We conducted a biomarker-based clinical study in eight FAP patients treated with enteric-coated low-dose Aspirin (100 mg daily for three months) to explore whether the drug targets mainly platelet cyclooxygenase (COX)-1 or affects extraplatelet cellular sources expressing COX-isozymes and/or off-target effects in colorectal adenomas. RESULTS: In FAP patients, low-dose Aspirin-acetylated platelet COX-1 at Serine529 (>70%) was associated with an almost complete inhibition of platelet thromboxane (TX) B2 generation ex vivo (serum TXB2). However, enhanced residual urinary 11-dehydro-TXB2 and urinary PGEM, primary metabolites of TXA2 and prostaglandin (PG)E2, respectively, were detected in association with incomplete acetylation of COX-1 in normal colorectal biopsies and adenomas. Proteomics of adenomas showed that Aspirin significantly modulated only eight proteins. The upregulation of vimentin and downregulation of HBB (hemoglobin subunit beta) distinguished two groups with high vs. low residual 11-dehydro-TXB2 levels, possibly identifying the nonresponders and responders to Aspirin. CONCLUSIONS: Although low-dose Aspirin appropriately inhibited the platelet, persistently high systemic TXA2 and PGE2 biosynthesis were found, plausibly for a marginal inhibitory effect on prostanoid biosynthesis in the colorectum. Novel chemotherapeutic strategies in FAP can involve blocking the effects of TXA2 and PGE2 signaling with receptor antagonists.

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

Vascular cyclooxygenase (COX)-2-dependent prostacyclin (PGI(2)) 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 PGI(2) 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 PGI(2), thromboxane (TX) A(2), and prostaglandin (PG) E(2), assessing their urinary enzymatic metabolites, 2,3-dinor-6-keto PGF(1α) (PGI-M), 11-dehydro-TXB(2) (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 TXA(2) generation was almost completely inhibited by pretreatment of platelets with aspirin, a preferential inhibitor of COX-1. In FAP, celecoxib profoundly suppressed PGE(2) and PGI(2) 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 PGE(2) by celecoxib may reduce tumor progression. However, the coincident depression of vascular PGI(2), in a context of enhanced TXA(2) biosynthesis, may modulate the attendant angiogenesis, contributing to variability in the chemopreventive efficacy of COX-2 inhibitors such as celecoxib.

Effects of estrogen on endothelial prostanoid production and cyclooxygenase-2 and heme oxygenase-1 expression.

We studied the effects of 17ß-estradiol (E2) (10, 40 nM) on 2 vasoprotective pathways, i.e. cyclooxygenase-2 (COX-2)-dependent prostanoids and the antioxidant heme oxygenase-1 (HO-1), in human umbilical vein endothelial cells (HUVEC) exposed for 6h to steady laminar shear stress (LSS, 10 dyn/cm²), characteristic of atherosclerotic lesion-protected areas. COX-2 was induced by LSS versus static condition (SC). E2 did not significantly affect COX-2 expression in HUVEC cultured in SC or exposed to LSS. Prostacyclin (PGI2) and prostaglandin (PG)E2 were induced while PGF(2α) was reduced by LSS. E2 caused no effect or a small reduction of prostanoid biosynthesis. In HUVEC cultured in SC or exposed to LSS, E2 10 nM caused a comparable HO-1 induction (35-45%) while E2 40 nM was 5-fold more potent in LSS-exposed HUVEC than in SC (290% and 58%, respectively). PGI2 receptor antagonist RO3244794 did not affect HO-1 induction by E2. In conclusion, E2 may restrain oxidant stress in the endothelium through HO-1 induction by a mechanism independent on PGI2 signaling.

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 aspirin's 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.

Antiplatelet Agents Affecting GPCR Signaling Implicated in Tumor Metastasis.

Metastasis requires that cancer cells survive in the circulation, colonize distant organs, and grow. Despite platelets being central contributors to hemostasis, leukocyte trafficking during inflammation, and vessel stability maintenance, there is significant evidence to support their essential role in supporting metastasis through different mechanisms. In addition to their direct interaction with cancer cells, thus forming heteroaggregates such as leukocytes, platelets release molecules that are necessary to promote a disseminating phenotype in cancer cells via the induction of an epithelial-mesenchymal-like transition. Therefore, agents that affect platelet activation can potentially restrain these prometastatic mechanisms. Although the primary adhesion of platelets to cancer cells is mainly independent of G protein-mediated signaling, soluble mediators released from platelets, such as ADP, thromboxane (TX) A2, and prostaglandin (PG) E2, act through G protein-coupled receptors (GPCRs) to cause the activation of more additional platelets and drive metastatic signaling pathways in cancer cells. In this review, we examine the contribution of the GPCRs of platelets and cancer cells in the development of cancer metastasis. Finally, the possible use of agents affecting GPCR signaling pathways as antimetastatic agents is discussed.

Inflammation and Cancer: From the Development of Personalized Indicators to Novel Therapeutic Strategies.

Colorectal (CRC) and hepatocellular carcinoma (HCC) are associated with chronic inflammation, which plays a role in tumor development and malignant progression. An unmet medical need in these settings is the availability of sensitive and specific noninvasive biomarkers. Their use will allow surveillance of high-risk populations, early detection, and monitoring of disease progression. Moreover, the characterization of specific fingerprints of patients with nonalcoholic fatty liver disease (NAFLD) without or with nonalcoholic steatohepatitis (NASH) at the early stages of liver fibrosis is necessary. Some lines of evidence show the contribution of platelets to intestinal and liver inflammation. Thus, low-dose Aspirin, an antiplatelet agent, reduces CRC and liver cancer incidence and mortality. Aspirin also produces antifibrotic effects in NAFLD. Activated platelets can trigger chronic inflammation and tissue fibrosis via the release of soluble mediators, such as thromboxane (TX) A2 and tumor growth factor (TGF)-ß, and vesicles containing genetic material (including microRNA). These platelet-derived products contribute to cyclooxygenase (COX)-2 expression and prostaglandin (PG)E2 biosynthesis by tumor microenvironment cells, such as immune and endothelial cells and fibroblasts, alongside cancer cells. Enhanced COX-2-dependent PGE2 plays a crucial role in chronic inflammation and promotes tumor progression, angiogenesis, and metastasis. Antiplatelet agents can indirectly prevent the induction of COX-2 in target cells by inhibiting platelet activation. Differently, selective COX-2 inhibitors (coxibs) block the activity of COX-2 expressed in the tumor microenvironment and cancer cells. However, coxib chemopreventive effects are hampered by the interference with cardiovascular homeostasis via the coincident inhibition of vascular COX-2-dependent prostacyclin biosynthesis, resulting in enhanced risk of atherothrombosis. A strategy to improve anti-inflammatory agents' use in cancer prevention could be to develop tissue-specific drug delivery systems. Platelet ability to interact with tumor cells and transfer their molecular cargo can be employed to design platelet-mediated drug delivery systems to enhance the efficacy and reduce toxicity associated with anti-inflammatory agents in these settings. Another peculiarity of platelets is their capability to uptake proteins and transcripts from the circulation. Thus, cancer patient platelets show specific proteomic and transcriptomic expression profiles that could be used as biomarkers for early cancer detection and disease monitoring.

Characterization of the acetylation of cyclooxygenase-isozymes and targeted lipidomics of eicosanoids in serum and colon cancer cells by the new aspirin formulation IP1867B versus aspirin in vitro.

Background: Aspirin(acetylsalicylic acid, ASA) is recommended for the secondary prevention of atherothrombotic events and has shown anticancer effects. The current enteric-coated drug formulation may reduce aspirin bioavailability. Liquid formulations could improve aspirin pharmacokinetics and pharmacodynamics. IP1867B is a liquid-aspirin formulation that combines three ingredients, ASA/triacetin/saccharin. Methods: ASA and IP1867B(L-ASA) were assessed in human serum(obtained by allowing to clot human whole blood at 37 °C for 1h), washed platelets, and colonic adenocarcinoma HCA7 cells on eicosanoid generation and COX-isozyme acetylation at Serine529 and 516 by LC-MS/MS. Results: In serum, ASA and L-ASA acted by selectively affecting COX-1-derived eicosanoids, including thromboxane(TX)B2. L-ASA was more potent in inhibiting serum TXB2, a known biomarker of aspirin antiplatelet effect, than ASA. However, ASA and L-ASA were equipotent to acetylate COX-1 in washed platelets and COX-2 in HCA7 cells. In HCA7 cells, ASA and L-ASA acted by inhibiting prostaglandin(PG)E2(the most abundant prostanoid) and TXB2 biosynthesis. In the presence of a high arachidonic acid concentration(100 µM), 15R-hydroxyeicosatetraenoic acid(HETE) was generated at baseline by cancer cell COX-2 and was only slightly enhanced by supratherapeutic concentrations of ASA(1 mM). In whole blood and HCA7 cells treated with ASA or L-ASA, 15-epi-lipoxin(LX)A4 were undetectable. Conclusion: IP1867B was more potent in affecting serum TXB2 generation than ASA. The relevance of this finding deserves evaluation in vivo in humans. In cancer cells, ASA and IP1867B acted by inhibiting PGE2 and TXB2 generation via the acetylation of COX-2. ASA and IP867B at clinically relevant concentrations did not substantially induce the biosynthesis of 15R-HETE and 15-epi-LXA4.