Luca Antonioli

Immunity, inflammation and cancer: A leading role for adenosine

Cancer is a complex disease that is dictated by both cancer cell-intrinsic and cell-extrinsic processes. Adenosine is an ancient extracellular signalling molecule that can regulate almost all aspects of tissue function. As such, several studies have recently highlighted a crucial role for adenosine signalling in regulating the various aspects of cell-intrinsic and cell-extrinsic processes of cancer development. This Review critically discusses the role of adenosine and its receptors in regulating the complex interplay among immune, inflammatory, endothelial and cancer cells during the course of neoplastic disease.

Safety concerns associated with the use of serotonin reuptake inhibitors and other serotonergic/noradrenergic antidepressants during pregnancy: A review

BACKGROUND There is ongoing debate about the safety of selective serotonin reuptake inhibitors (SSRIs) and other serotonergic/noradrenergic antidepressants when used during pregnancy. OBJECTIVE This article reviews the available literature on the main safety concerns associated with the use of SSRIs and other serotonergic/noradrenergic antidepressants (serotonin-norepinephrine reuptake inhibitors, norepinephrine reuptake inhibitors, noradrenergic and specific serotonergic antidepressants) during pregnancy. METHODS English-language reports of analytical and descriptive studies, including case reports, case series, and meta-analyses, were identified through searches of MEDLINE, EMBASE, and PsycINFO (1966-April 2009). The search terms were fluoxetine, paroxetine, sertraline, Citalopram, escitalopram, fluvoxamine, venlafaxine, mirtazapine, reboxetine, duloxetine, SSRI, SNRI, NaSSA, and NRI in association with depression, pregnancy, prenatal exposure, miscarriage, spontaneous abortion, malformation, in utero exposure, and neonatal complications. RESULTS Paroxetine has been associated with significant risks of major malformation, particularly cardiac defects, when used during pregnancy. Significant associations between maternal exposure to SSRIs and both persistent pulmonary hypertension of the newborn and a self-limiting neonatal behavioral syndrome have been reported in a number of recent original studies and meta-analyses. Some studies have suggested a relationship between the use of SSRIs or other serotonergic/noradrenergic antidepressants and the occurrence of miscarriage, although these studies had methodologic limitations that affected the strength of the data. Evidence for a possible association between in utero exposure to SSRIs or other serotonergic/noradrenergic antidepressants and alterations in neurobehavioral development, bleeding, and QTc-interval prolongation is currently weak. CONCLUSION The available evidence suggests that SSRIs and other serotonergic/noradrenergic antidepressants should be used with caution during pregnancy, with careful follow-up of infants exposed to these agents in utero.

Regulation of enteric functions by adenosine: pathophysiological and pharmacological implications.

The wide distribution of ATP and adenosine receptors as well as enzymes for purine metabolism in different gut regions suggests a complex role for these mediators in the regulation of gastrointestinal functions. Studies in rodents have shown a significant involvement of adenosine in the control of intestinal secretion, motility and sensation, via activation of A1, A2A, A2B or A3 purinergic receptors, as well as the participation of ATP in the regulation of enteric functions, through the recruitment of P2X and P2Y receptors. Increasing interest is being focused on the involvement of ATP and adenosine in the pathophysiology of intestinal disorders, with particular regard for inflammatory bowel diseases (IBDs), intestinal ischemia, post-operative ileus and related dysfunctions, such as gut dysmotility, diarrhoea and abdominal discomfort/pain. Current knowledge suggests that adenosine contributes to the modulation of enteric immune and inflammatory responses, leading to anti-inflammatory actions. There is evidence supporting a role of adenosine in the alterations of enteric motor and secretory activity associated with bowel inflammation. In particular, several studies have highlighted the importance of adenosine in diarrhoea, since this nucleoside participates actively in the cross-talk between immune and epithelial cells in the presence of diarrhoeogenic stimuli. In addition, adenosine exerts complex regulatory actions on pain transmission at peripheral and spinal sites. The present review illustrates current information on the role played by adenosine in the regulation of enteric functions, under normal or pathological conditions, and discusses pharmacological interventions on adenosine pathways as novel therapeutic options for the management of gut disorders and related abdominal symptoms.

Atorvastatin Prevents Endothelial Dysfunction in Mesenteric Arteries From Spontaneously Hypertensive Rats: Role of Cyclooxygenase 2-Derived Contracting Prostanoids

We investigated the effect of atorvastatin on cyclooxygenase (COX) contribution to endothelial dysfunction in spontaneously hypertensive rat (SHR) mesenteric resistance arteries. Atorvastatin (10 mg/kg per day, oral gavage) or its vehicle was administered for 2 weeks to male SHR or Wistar-Kyoto rats. Endothelial function of mesenteric arteries was assessed by pressurized myograph. In Wistar-Kyoto rats, relaxation to acetylcholine was inhibited by NG-nitro-l-arginine methyl ester and unaffected by SC-560 (COX-1 inhibitor), DuP-697 (COX-2 inhibitor), or ascorbic acid. In SHRs, the response to acetylcholine was attenuated, less sensitive to NG-nitro-l-arginine methyl ester, unaffected by SC-560, and enhanced by DuP-697 or SQ-29548 (thromboxane-prostanoid receptor antagonist) to a similar extent. Endothelium-dependent relaxation was normalized by ascorbic acid or apocynin (NADPH oxidase inhibitor), which also restored the inhibition by NG-nitro-l-arginine methyl ester. In atorvastatin-treated SHRs, relaxation to acetylcholine was normalized, fully sensitive to NG-nitro-l-arginine methyl ester, and not affected by SC-560, DuP-697, SQ 29548, or antioxidants. Dihydroethidium assay showed an increased intravascular superoxide generation in SHRs, which was abrogated by atorvastatin. RT-PCR revealed a COX-2 induction in SHR arteries, which was downregulated by atorvastatin. The release of prostacyclin and 8-isoprostane was higher from SHR than Wistar-Kyoto mesenteric vessels. COX-2 inhibition and apocynin decreased 8-isoprostane without affecting prostacyclin levels. Atorvastatin increased phosphorylated extracellular signal–regulated kinase 1/2, pAkt, peNOS1177, and inducible NO synthase levels in SHR mesenteric vessels and decreased 8-isoprostane release. In conclusion, COX-2–derived 8-isoprostane contributes to endothelial dysfunction in SHR mesenteric arteries. Atorvastatin restores NO availability by increasing phosphorylated extracellular signal–regulated kinase 1/2, pAkt, peNOS1177, and inducible NO synthase levels and by abrogating vascular NADPH oxidase–driven superoxide production, which also results in a downregulation of COX-2–dependent 8-isoprostane generation.

Cyclooxygenase-1 Is Involved in Endothelial Dysfunction of Mesenteric Small Arteries From Angiotensin II–Infused Mice

Angiotensin II induces endothelial dysfunction by reducing NO availability and increasing reactive oxygen species. We assessed whether cyclooxygenase (COX)-1 or COX-2 participate in the angiotensin II-induced endothelial dysfunction in murine mesenteric small arteries and examined the role of reduced nicotinamide-adenine dinucleotide phosphate-dependent reactive oxygen species production. Mice received angiotensin II (600 ng/kg per minute, SC), saline (controls), angiotensin II + apocynin (reduced nicotinamide-adenine dinucleotide phosphate oxidase inhibitor, 2.5 mg/day), or apocynin alone for 2 weeks. Endothelial function of mesenteric arteries was assessed by pressurized myograph. In controls, acetylcholine-induced relaxation was inhibited by NG-monomethyl-l-arginine and unaffected by DFU (COX-2 inhibitor), SC-560 (COX-1 inhibitor), or ascorbic acid. In angiotensin II-infused animals, the attenuated response to acetylcholine was less sensitive to NG-monomethyl-l-arginine, unaffected by DFU, and enhanced by SC-560 and, similarly, by SQ-29548, a thromboxane-prostanoid receptor antagonist. Moreover, response to acetylcholine was unchanged by ozagrel, a thromboxane synthase inhibitor, and normalized by ascorbic acid. Apocynin prevented the angiotensin II-induced vascular dysfunctions. In angiotensin II-infused mice, RT-PCR analysis showed a significant COX-2 downregulation, whereas COX-1 expression was upregulated. These changes were unaffected by apocynin. Modulation of COX isoform by angiotensin II was also documented by immunohistochemistry. In small mesenteric vessels, the reduced NO availability and oxidant excess, which characterize endothelial dysfunction secondary to angiotensin II, are associated with a reduced COX-2 and an increased COX-1 function and expression. Angiotensin II causes an oxidative stress-independent COX-1 overexpression, whereas angiotensin II-mediated oxidant excess production stimulates COX-1 activity to produce a contracting prostanoid endowed with agonist activity on thromboxane-prostanoid receptors.

Pharmacological modulation of adenosine system: Novel options for treatment of inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) are chronic disorders resulting from abnormal and persistent immune responses which lead to severe tissue injury and disturbances in digestive motor/secretory functions. At present, pharmacotherapy represents the cornerstone for the management of IBDs, and recent advances in understanding the immunopathogenesis of intestinal inflammation suggest the adenosine system as an attractive target for development of novel drugs against gut inflammatory disorders. Consistent evidence indicates that adenosine plays a relevant role in the regulation of immune system via interaction with specific cell‐membrane G‐protein‐coupled receptors (A1, A2a, A2b, and A3). Moreover, this nucleoside is implicated in the control of enteric neurotransmission and gut motor functions. In the presence of inflammation, the adenosine system acts as a sensible sensor apparatus, which, through dynamic modifications in the expression of ecto‐enzymes and purinergic receptors, adapts its metabolism to tissue health status and contributes to the mechanisms deputed to the protection of tissues against inflammatory injuries. In keeping with these concepts, it is becoming increasingly appreciated that drugs targeted on adenosine receptors or enzymes responsible for adenosine catabolism can exert beneficial effects on experimental models of intestinal inflammation. This review aims to discuss the role of adenosine in the regulation of enteric immune responses and gut neuromuscular functions in the presence of inflammation, as well as to highlight the mechanisms through which the pharmacological modulation of adenosine pathways may have potential applications for the therapeutic management of IBDs.

Adenosine Deaminase in the Modulation of Immune System and its Potential as a Novel Target for Treatment of Inflammatory Disorders

The adenosine pathway is a powerful evolutionarily selected mechanism aimed at a fine modulation of inflammatory responses and protection of tissues from injuries. Adenosine exerts its modulatory effects via interaction with G protein-coupled receptors, designated as A(1), A(2A), A(2B) and A(3). In this regard, extracellular adenosine concentrations are critical in determining its ability of regulating several biological functions. The levels achieved by adenosine in close proximity of its receptors are strictly regulated by a variety of dynamic mechanisms, including intracellular and extracellular biosynthesis, transport and metabolism, based on tissue energy status. In this context, the catabolic enzyme adenosine deaminase (ADA) represents a critical checkpoint in the regulation of extracellular adenosine levels and, consequently, in the control of receptor stimulation, thus playing a pivotal role in the modulation of purinergic responses to several pathophysiological events, such as chronic pulmonary diseases, rheumatoid arthritis, inflammatory bowel diseases and sepsis. This article reviews current data on the role played by ADA in the regulation of immune system activity through its modulation of adenosine pathways. Particular attention has been paid to the involvement of ADA in the pathophysiology of relevant inflammatory diseases. In addition, the interest in designing and developing novel ADA inhibitors, as new tools potentially useful for the therapeutic management of inflammatory disorders, has been discussed.

Adenosine and inflammation: what's new on the horizon?

Adenosine contributes to the maintenance of tissue integrity by modulating the immune system. Encouraging results have emerged with adenosine receptor ligands for the management of several inflammatory conditions in preclinical and clinical settings. However, therapeutic applications of these drugs are sometimes complicated by the occurrence of serious adverse effects. The scientific community is making intensive efforts to design novel adenosine receptor ligands endowed with greater selectivity or to develop innovative compounds acting as allosteric receptor modulators. In parallel, research is focusing on novel pharmacological entities (designated as adenosine-regulating agents) that can increase, in a site- and event-specific manner, adenosine concentrations at the inflammatory site, thereby minimizing the adverse systemic effects of adenosine.

Role of cyclooxygenases 1 and 2 in the modulation of neuromuscular functions in the distal colon of humans and mice

Background: Cyclooxygenase isoforms (COX-1, COX-2) may exert differential regulatory actions on enteric motor functions under normal or pathological conditions. Aims: To examine the occurrence and functions of COX-1 and COX-2 in the neuromuscular compartment of normal distal colon using human and murine tissue. Methods: Gene expression (human, mouse), protein expression (human), gene deletion (mouse), and the effects of dual and isoform specific COX inhibitors on in vitro motility (human, mouse) were investigated. Results: Reverse transcription-polymerase chain reaction (RT-PCR) showed mRNA expression of COX-1 and COX-2 in human and wild-type mouse colonic muscle whereas only COX-2 or COX-1 was detected in COX-1 or COX-2 knockout animals. Immunohistochemistry localised both isoforms in neurones of myenteric ganglia, COX-1 in circular layer myocytes, and COX-2 in longitudinal muscle. Indomethacin (COX-1/COX-2 inhibitor), SC-560 (COX-1 inhibitor), or DFU (COX-2 inhibitor) enhanced atropine sensitive electrically induced contractions of human longitudinal muscle. The most prominent actions were recorded with indomethacin or SC-560 plus DFU. These results were confirmed under pharmacological blockade of non-cholinergic nerves. Atropine sensitive contractions evoked by carbachol in the presence of tetrodotoxin were enhanced by indomethacin or DFU but not by SC-560. In wild-type mice, contractile responses to electrical stimulation were enhanced by indomethacin, SC-560, or DFU. SC-560 potentiated electrically induced contractions in COX-2, but not COX-1, knockout mice. In contrast, DFU enhanced the contractions elicited by electrical stimuli in COX-1, but not in COX-2, knockout mice. Conclusions: These results indicate that COX-1 and COX-2 are expressed in the neuromuscular compartment of normal human colon where they modulate cholinergic excitatory control of colonic motility at prejunctional and postjunctional sites, respectively.

Adenosine signalling in diabetes mellitus—pathophysiology and therapeutic considerations

Adenosine is a key extracellular signalling molecule that regulates several aspects of tissue function by activating four G-protein-coupled receptors, A1, A2A, A2B and A1 adenosine receptors. Accumulating evidence highlights a critical role for the adenosine system in the regulation of glucose homeostasis and the pathophysiology of type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Although adenosine signalling is known to affect insulin secretion, new data indicate that adenosine signalling also contributes to the regulation of β-cell homeostasis and activity by controlling the proliferation and regeneration of these cells as well as the survival of β cells in inflammatory microenvironments. Furthermore, adenosine is emerging as a major regulator of insulin responsiveness by controlling insulin signalling in adipose tissue, muscle and liver; adenosine also indirectly mediates effects on inflammatory and/or immune cells in these tissues. This Review critically discusses the role of the adenosine–adenosine receptor system in regulating both the onset and progression of T1DM and T2DM, and the potential of pharmacological manipulation of the adenosinergic system as an approach to manage T1DM, T2DM and their associated complications.