Treatment of glaucoma by prostaglandin agonists and beta-blockers in combination directly reduces pro-fibrotic gene expression in trabecular meshwork.

Prostaglandin analogues (PG), beta-blockers (BB) or their combination (PG+BB) are used primarily to reduce the intraocular pressure (IOP) pathologically associated with glaucoma. Since, fibrosis of the trabecular meshwork (TM) is a major aetiological factor in glaucoma, we studied the effect of these drugs on fibrosis-associated gene expression in TM of primary glaucoma patients. In the present study, TM and iris of primary open-angle (n = 32) and angle-closure (n = 37) glaucoma patients were obtained surgically during trabeculectomy and categorized based on the type of IOP-lowering medications use as PG, BB or PG+BB. mRNA expression of pro-fibrotic and anti-fibrotic genes was quantified using qPCR in these tissues. The gene expression levels of pro-fibrotic genes were significantly lower in PG+BB as compared to other groups. These observations and underlying signalling validated in vitro in human TM cells also showed reduced fibrotic gene and protein expression levels following PG+BB treatment. In conclusion, it is observed that PG+BB combination rather than their lone use renders a reduced fibrotic status in TM. This further suggests that IOP-lowering medications, in combination, would also modulate fibrosis-associated molecular changes in the TM, which may be beneficial for maintaining aqueous out-flow mechanisms over the clinical treatment duration.

Discovery, characterization and clinical utility of prostaglandin agonists for the treatment of glaucoma.

Topical ophthalmic formulations of analogues of the endogenous arachidonic acid cyclooxygenase metabolite, PGF2α , are the standard of care treatment for the blinding disease glaucoma. These are the most potent and efficacious medical therapies for lowering intraocular pressure (IOP), the most important risk factor identified for disease progression. They have few side effects and offer the convenience of once-a-day dosing. It was initially believed that endogenous PGs raised IOP and caused substantial ocular surface adverse effects. However, carefully designed experiments demonstrated that esterification of the carboxylic acid afforded potent and efficacious topical ocular hypotensive activity. The final hurdle to be overcome was improvement of the side effect profile. A hypothesis was advanced that the IOP-lowering effect of PGF2α isopropyl ester was due to activation of its cognate PG-FP receptor, while side effects were largely due to promiscuous interaction with other PG receptors. This hypothesis was validated by modification of the ω chain (carbons 13-20) to a phenyl group. This provided the first marketed FP-class PG agonist analogue (FP-PGA) ocular hypotensive agent, latanoprost. Since the introduction of latanoprost into clinical medicine to lower and control IOP, a number of additional FP-PGAs have been discovered, characterized and marketed, including travoprost, tafluprost, unoprostone isopropyl ester and bimatoprost (an amide). LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Hechos en el tratamiento de la hipertensión arterial pulmonar asociada a la enfermedad mixta del tejido conectivo / Facts in treatment of pulmonary arterial hypertension associated with mixed connective tissue disease

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The Biological Enhancement of Spinal Fusion for Spinal Degenerative Disease.

In this era of aging societies, the number of elderly individuals who undergo spinal arthrodesis for various degenerative diseases is increasing. Poor bone quality and osteogenic ability in older patients, due to osteoporosis, often interfere with achieving bone fusion after spinal arthrodesis. Enhancement of bone fusion requires shifting bone homeostasis toward increased bone formation and reduced resorption. Several biological enhancement strategies of bone formation have been conducted in animal models of spinal arthrodesis and human clinical trials. Pharmacological agents for osteoporosis have also been shown to be effective in enhancing bone fusion. Cytokines, which activate bone formation, such as bone morphogenetic proteins, have already been clinically used to enhance bone fusion for spinal arthrodesis. Recently, stem cells have attracted considerable attention as a cell source of osteoblasts, promising effects in enhancing bone fusion. Drug delivery systems will also need to be further developed to assure the safe delivery of bone-enhancing agents to the site of spinal arthrodesis. Our aim in this review is to appraise the current state of knowledge and evidence regarding bone enhancement strategies for spinal fusion for degenerative spinal disorders, and to identify future directions for biological bone enhancement strategies, including pharmacological, cell and gene therapy approaches.

Decreased vasorelaxation induced by iloprost during acute inflammation in human internal mammary artery.

Cyclooxygenase-2 (COX-2) induction in human internal mammary arteries (IMA) under inflammatory conditions has been associated with attenuated norepinephrine (NE)-induced vasoconstriction. This effect was associated with increased prostaglandin (PG) E2 and prostacyclin (PGI2) releases. The present study was designed to assess the role of these PG and their receptors (EP and IP, respectively) on the vascular reactivity during acute inflammation. Isolated IMA were cultured in the absence (Control conditions) or presence (Inflammatory conditions) of both interleukin-1 beta (IL-1ß) and lipopolysaccharide (LPS). The vasorelaxation and the increased content of cyclic adenosine monophosphate (cAMP) induced by iloprost, a PGI2 analogue, were significantly reduced under inflammatory conditions and restored in preparations cultured with the IP antagonist (CAY10441). Decreased cAMP levels under inflammatory conditions are due to at least increased phosphodiesterase (PDE) 4B expression. On the other hand, PGE2, thromboxane analogues and EP agonists-induced vasoconstrictions were not affected under inflammatory conditions. No vasorelaxation was observed with PGD2, PGE2 or the EP2/4 agonists in pre-contracted IMA. Finally, using RT-qPCR and immunohistochemistry, the COX-2, IP receptor and PGI2 synthase (PGIS) were detected. A significant increase of COX-2 and moderate increase of IP mRNA expression was observed under inflammatory conditions, whereas PGIS mRNA level was not affected. This study demonstrates that PGI2/IP receptor signalling and PGI2-induced relaxation are impaired in human IMA during acute inflammation, whereas the responses induced by other prostanoids are not affected. These results could explain some of the mechanisms of vascular dysfunction reported in inflammatory conditions.

Leukotriene production profiles and actions in the bovine endometrium during the oestrous cycle.

We have previously shown the influence of leukotrienes (LTs) on reproductive functions in vivo: LTB4 is luteotrophic and supports corpus luteum function inducing PGE2 and progesterone (P4) secretion, whereas LTC4 is luteolytic and stimulates PGF2α secretion in cattle. The aim of this study was to examine expression and production profiles of LTs and their actions in the endometrium. LT receptors (LTB4R for LTB4 and CysLTR2 for LTC4), 5-lipoxygenase (LO), 12-LO synthase (LTCS) and LTA4 hydrolase (LTAH) mRNA and protein expression, as well as LT production were measured in bovine endometrial tissue during the luteal phases of the oestrous cycle. The action of LTs on uterine function was studied by measuring the level of PGs after stimulating uterine slices with LTs on Days 8-10 of the cycle. Expression of 5-LO and LTB4R mRNA and protein were highest on Days 2-4 of the cycle, while CysLTR2 and LTCS were highest on Days 16-18 (P<0.05). LTB4 concentration was highest on Days 2-4 of the cycle, whereas the greatest LTC4 level was on Days 16-18 (P<0.05). Both LTB4 and C4 increased the content of PGE2 and F2α in endometrial slices at a dose of 10(-7)M (P<0.05). In summary, mRNA expression and activation of receptors for LTB4 and production occur in the first part of the cycle, whereas LTC4 and its receptors predominate at the end of the cycle. The 12-LO and 5-LO pathways are complementary routes of LT production in the bovine uterus.

Interferon-γ stimulates human follicular dendritic cell-like cells to produce prostaglandins via the JAK-STAT pathway.

IFN-γ plays a critical role in the regulation of innate and adaptive immunity. Paying attention to the emerging role of prostaglandins (PGs) as immune regulators, we attempted to establish the effect of IFN-γ on PG production in human follicular dendritic cell-like HK cells and the underlying signaling pathway by using RNA interference technology. IFN-γ induced COX-2 protein expression in HK cells in a time- and dose-dependent manner, which was not observed in peripheral blood monocytes. Although IFN-γ induced phosphorylation of STAT1, STAT3, and STAT5, only STAT1 was essential for the COX-2 augmentation. The JAK kinases responsible for IFN-γ-triggered STAT1 phosphorylation were JAK1 and JAK2, which were also required for the COX-2 induction. The essential requirement of JAK1 and JAK2 was verified by confocal microscopic analysis, since STAT1 phosphorylation and nuclear translocation were impaired in HK cells with these two kinases knocked down. Finally, we demonstrated that JAK1, JAK2, and STAT1 were indispensable for the actual enhancement of PG production in response to IFN-γ stimulation. These results provide a novel insight into our understanding of IFN-γ under inflammatory conditions and support the emerging concept of PGs as important immune regulators.

The prostaglandin agonist beraprost aggravates doxorubicin-mediated apoptosis by increasing iNOS expression in cardiomyocytes.

Doxorubicin (DOX) is widely used as an anti-cancer agent although it causes irreversible cardiomyopathy by increasing oxidative stress and deregulating nitric oxide production. Beraprost (BPS), a stable prostacyclin (PGI2) analog, is a potent vasodilator that has beneficial effects on myocardial ischemia. The objectives of the present study were to delineate the uncertain effects of prostcyclin therapy on DOX induced cardiomyopathy and to explore the mechanisms underlying PGI2 and DOX interaction. For this reason, we stimulated endogenous PGI2 production using bicistronic COX-1/PGIS gene transfer and BPS supplementation, and investigated the effects on DOX-induced cardiomyopathy. Caspase-dependent protein content, lactate dehydrogenase (LDH), DNA fragmentation, and TUNEL positive cells were elevated in DOX-treated cardiomyocytes. These indicators were further elevated by adenovirus-COX- 1/PGIS transfection or BPS supplementation. In addition, PGI2 overexpression further increased iNOS expression and superoxide accumulation in cardiomyocytes compared with DOX alone, which may be the reason for aggravated cytotoxicity. Moreover, BPS can induce cAMP response elements (CRE) binding to the iNOS promoter and phospho- cAMP response element binding protein (CREB) expression in a cyclic AMP-dependent manner. Our in vivo studies show that MnTBAP and aminoguanidine treatment of DOX and BPS co-administered in mice can attenuate caspase-3 and PARP-1 protein expression, and improve mouse survival, as observed in the iNOS gene-deleted mice. In conclusion, we demonstrated that BPS or adv-COX-1/PGIS increases PGI2 levels through iNOS expression and peroxynitrite production, via CREB protein phosphorylation; thereby aggravating DOX-mediated cardiotoxicity.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress.

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

Anabolic agents and bone quality.

BACKGROUND: The definition of bone quality is evolving particularly from the perspective of anabolic agents that can enhance not only bone mineral density but also bone microarchitecture, composition, morphology, amount of microdamage, and remodeling dynamics. QUESTIONS/PURPOSES: This review summarizes the molecular pathways and physiologic effects of current and potential anabolic drugs. METHODS: From a MEDLINE search (1996-2010), articles were identified by the search terms "bone quality" (1851 articles), "anabolic agent" (5044 articles), "PTH or parathyroid hormone" (32,229 articles), "strontium" or "strontium ranelate" (283 articles), "prostaglandin" (77,539 articles), and "statin" or "statins" (14,233 articles). The search strategy included combining each with the phrase "bone quality." Another more limited search aimed at finding more novel potential agents. RESULTS: Parathyroid hormone is the only US Food and Drug Administration-approved bone anabolic agent in the United States and has been the most extensively studied in in vitro animal and human trials. Strontium ranelate is approved in Europe but has not undergone Food and Drug Administration trials in the United States. All the studies on prostaglandin agonists have used in vivo animal models and there are no human trials examining prostaglandin agonist effects. The advantages of statins include the long-established advantages and safety profile, but they are limited by their bioavailability in bone. Other potential pathways include proline-rich tyrosine kinase 2 (PYK2) and sclerostin (SOST) inhibition, among others. CONCLUSIONS: The ongoing research to enhance the anabolic potential of current agents, identify new agents, and develop better delivery systems will greatly enhance the management of bone quality-related injuries and diseases in the future.

Prostaglandins in pathogenesis and treatment of multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) characterized by inflammation, demyelination, axonal loss, and gliosis. The inflammatory lesions are manifested by a large infiltration and a heterogeneous population of cellular and soluble mediators of the immune system, such as T cells, B cells, macrophages, and microglia, as well as a broad range of cytokines, chemokines, antibodies, complement, and other toxic substances. Prostaglandins (PGs) are arachidonic acid-derived autacoids that have a role in the modulation of many physiological systems including the CNS, respiratory, cardiovascular, gastrointestinal, genitourinary, endocrine, and immune systems. PG production is associated with inflammation, a major feature in MS that is characterized by the loss of myelinating oligodendrocytes in the CNS. With respect to the role of PGs in the induction of inflammation, they can be effective mediators in the pathophysiology of MS. Thus use of agonists or antagonists of PG receptors may be considered as a new therapeutic protocol in MS. In this review, we try to clarify the role of PGs in immunopathology and treatment of MS.

[New developments in glaucoma medical treatment]. / Nuevos desarrollos en el tratamiento médico del glaucoma.

The medical treatment of glaucoma has undergone significant development in recent years. Research in this field is focused on improving pre-existing drugs and on the development of new molecules. In relation to commercial drugs, there is a trend to improve local tolerance, using less toxic preservatives as in the case of sofZIA in travoprost, and eliminating the preservatives as in tafluprost. The development of new, fixed combinations of commercial drugs could also enhance their administration and therapeutic compliance. There is also intense research activity in the search for new therapeutic groups for glaucoma treatment. Calcium channel-blockers such as lomerizine do not seem to affect systemic hypotension, while topical calcium-blockers like flunarizine and iganidipine are also under research. Endothelin 1 antagonists such as sulfisoxazole and bunazosine could be also useful in the treatment of glaucoma. In the renin angiotensin system, angiotensin (1-7) and olmesartan are under investigation for use in glaucoma patients. Trabecular drugs such as Rho-kinase inhibitors could be effective on the pathogenic mechanism of primary open angle glaucoma. Finally, topical mifepristone, an antagonist of glucocorticoid receptors, is under evaluation for corticosteroid-induced elevated intraocular pressure (Arch Soc Esp Oftalmol 2009; 84: 491-500).

Prostaglandin regulation of gastric slow waves and peristalsis.

Gastric emptying depends on functional coupling of slow waves between the corpus and antrum, to allow slow waves initiated in the gastric corpus to propagate to the pyloric sphincter and generate gastric peristalsis. Functional coupling depends on a frequency gradient where slow waves are generated at higher frequency in the corpus and drive the activity of distal pacemakers. Simultaneous intracellular recording from corpus and antrum was used to characterize the effects of PGE(2) on slow waves in the murine stomach. PGE(2) increased slow-wave frequency, and this effect was mimicked by EP(3), but not by EP(2), receptor agonists. Chronotropic effects were due to EP(3) receptors expressed by intramuscular interstitial cells of Cajal because these effects were not observed in W/W(V) mice. Although the integrated chronotropic effects of EP(3) receptor agonists were deduced from electrophysiological experiments, no clear evidence of functional uncoupling was observed with two-point electrical recording. Gastric peristalsis was also monitored by video imaging and spatiotemporal maps to study the impact of chronotropic agonists on propagating contractions. EP(3) receptor agonists increased the frequency of peristaltic contractions and caused ectopic sites of origin and collisions of peristaltic waves. The impact of selective regional application of chronotropic agonists was investigated by use of a partitioned bath. Antral slow waves followed enhanced frequencies induced by stimulation of the corpus, and corpus slow waves followed when slow-wave frequency was elevated in the antrum. This demonstrated reversal of slow-wave propagation with selective antral chronotropic stimulation. These studies demonstrate the impact of chronotropic agonists on regional intrinsic pacemaker frequency and integrated gastric peristalsis.

Hormone profiles and treatments in the late pregnant mare.

Evaluation of hormone profiles in late pregnancy is one of the major determinants of fetoplacental compromise in equine clinical practice. Use of hormone therapies is subjective and reflects, to a large extent, our lack of understanding about the endocrine relations between the mare, placenta, and fetus. This article describes the normal endocrine events in late gestation, the abnormal hormone patterns associated with fetoplacental dysfunction, and the hormone interventions that are currently used or could be used to improve pregnancy outcome.

Roles of endogenous prostaglandins and cyclooxygenase isozymes in healing of indomethacin-induced small intestinal lesions in rats.

The role of prostaglandins (PGs)/cyclooxygenase (COX) in the healing of indomethacin-induced small intestinal ulcers was examined in rats. Animals were given indomethacin (10 mg/kg s.c.) and killed 1, 2, 3, 5, and 7 days later. Indomethacin (2 mg/kg), 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC560; COX-1 inhibitor; 3 mg/kg), and rofecoxib (COX-2 inhibitor; 3 mg/kg) were given p.o. once daily for 6 days, during the first 3 days or last 3 days of the experimental period. All COX inhibitors given for 6 days significantly impaired the healing of these ulcers. Healing was also impaired by rofecoxib given for the first 3 days or by SC560 given for the last 3 days. The expression of COX-2 mRNA in the intestine was up-regulated after ulceration, persisting for 3 days and dissipating thereafter. Mucosal PGE2 contents decreased within 3 h after ulceration, recovered 24 h later, and increased above normal 1 approximately 3 days later. The PGE2 content at 4 days after ulceration was decreased by rofecoxib but not SC560, whereas that at 7 days was suppressed by SC560 but not rofecoxib. Vascular content in the ulcerated mucosa decreased when the healing was impaired by COX inhibitors. The deleterious effect of indomethacin on healing was mimicked by a prostacyclin E receptor (EP) 4 antagonist and reversed by coadministration of PGE2 as well as an EP4 agonist. In conclusion, endogenous PGs play a role in the healing of intestinal ulcers through EP4 receptors, yet the COX isozyme involved differs depending on the stage of healing; COX-2 in the early stage and COX-1 in the late stage.

Duodenal secretion in humans mediated by the EP4 receptor subtype.

AIM: Assessment of functional EP receptor subtypes involved in PGE2-induced secretion in human duodenum. The spectrum of activities by PGE2 in mammals, including cytoprotective bicarbonate secretion in duodenum, is mediated through four G protein-coupled receptor subtypes (EP1-EP4). METHODS: Biopsies from the second part of duodenum from patients undergoing endoscopy were mounted in modified Ussing chambers. Basal and stimulated short circuit current (SCC) and slope conductance (SG) were measured. Dose-response relations for PGE2 and subtype receptors EP1/EP3 (sulprostone), EP2 (butaprost), and EP4 (1-OH PGE1) were assessed by cumulated doses of single agonists. RESULTS: PGE2 caused a dose-dependent increase in SCC, maximum 101 +/- 20 microA cm(-2) with an EC50 of 35.6 +/- 5.8 nm (n = 3). Likewise 1-OH PGE1 caused a dose-dependent SCC increase, maximum 63.3 +/- 28.6 microA cm(-2) with an EC50 of 56.7 +/- 7.2 nm (n = 3). 1-OH PGE1 at 500 nm increased SCC by 18.0 +/- 3.0 microA cm(-2) (n = 10) and SG by 2.9 +/- 0.4 mS cm(-2) (n = 6). Sulprostone (n = 6) and butaprost (n = 6) had no effects on SCC or SG. SCC was inhibited 31.4 +/- 13.2% (n = 10) by bumetanide (25 microM serosa) and 18.6 +/- 5.8% (n = 10) by acetazolamide (250 microM lumen). Diphenylamine-2-carboxylate (DPC) (250 microM mucosa) and SITS (10 microM mucosa) had almost no effect. CONCLUSIONS: Effects of PGE2 on secretion in the second part of human duodenum is mediated through the EP4 receptor and not through EP1, EP2, or EP3.

A new method for measuring inhibition of platelet function by nonsteroidal antiinflammatory drugs.

Aspirin is widely used to help prevent vascular occlusion caused by atherosclerotic vascular disease. We used a platelet-aggregation assay (PAA) to evaluate the reliability of a proprietary platelet agonist, platelet prostaglandin agonist (PPA), to detect the amount of platelet inhibition induced by four different classes of nonsteroidal antiinflammatory drugs (NSAIDs) with antiplatelet effects. Twenty normal donors were evaluated before and 24 hours after ingestion of 325 mg of aspirin. With 125 micromol/L PPA, the slope of the PPA-PAA curve completely differentiated aspirin-treated from normal platelets. The aspirin platelet slope, 27.9 +/- 2.0 (range 5.5-47), was significantly decreased (P <.001) compared with the findings before administration of aspirin, 75 +/- 3.1 (range 50-125). Additionally, the time elapsed before 50% platelet aggregation (T(50)) with aspirin, 10.1 +/- 0.7 minutes (range 4.7-17), was significantly prolonged (P <.05) compared with the mean time before administration of aspirin (4.2 +/- 0.2 minutes, range 1.7-6.4). Aspirin in a daily dosage of 325 mg for 14 days produced significantly greater inhibition of PPA-PAA than that induced by a single 325-mg dose (P <.001). The long-term platelet-inhibitory effects of aspirin in 9 normal volunteers were evaluated with PPA-PAA 2, 8, 24, 48, 72, and 96 hours after a single dose of aspirin, 81 or 325 mg. Compared with the preaspirin slope, 79.6 +/- 1.9, the maximal decrease in slope occurred after 2 hours for both 81 mg (61.3 +/- 6.7) and 325 mg (12.1 +/- 1.8). The decreased slopes and increased T(50) observed at 2, 8, and 24 hours (P <.001) reflected the greater degree of platelet inhibition with 325 mg than with 81 mg aspirin. Inhibition of PPA-PAA was observed with nonaspirin nonsteroidal antiinflammatory drugs (NNSAIDs), but, compared with aspirin, the inhibition was minimal. PPA-PAA may be used to help measure the magnitude of NSAID-induced inhibition of platelets.

Prostaglandins and leukotrienes: advances in eicosanoid biology.

Prostaglandins and leukotrienes are potent eicosanoid lipid mediators derived from phospholipase-released arachidonic acid that are involved in numerous homeostatic biological functions and inflammation. They are generated by cyclooxygenase isozymes and 5-lipoxygenase, respectively, and their biosynthesis and actions are blocked by clinically relevant nonsteroidal anti-inflammatory drugs, the newer generation coxibs (selective inhibitors of cyclooxygenase-2), and leukotriene modifiers. The prime mode of prostaglandin and leukotriene action is through specific G protein-coupled receptors, many of which have been cloned recently, thus enabling specific receptor agonist and antagonist development. Important insights into the mechanisms of inflammatory responses, pain, and fever have been gleaned from our current understanding of eicosanoid biology.

Prostaglandins and cyclooxygenases [correction of cycloxygenases] in the spinal cord.

The spinal cord is one of the sites where non-steroidal anti-inflammatory drugs (NSAIDs) act to produce analgesia and antinociception. Expression of cyclooxygenase(COX)-1 and COX-2 in the spinal cord and primary afferents suggests that NSAIDs act here by inhibiting the synthesis of prostaglandins (PGs). Basal release of PGD(2), PGE(2), PGF(2alpha) and PGI(2) occurs in the spinal cord and dorsal root ganglia. Prostaglandins then bind to G-protein-coupled receptors located in intrinsic spinal neurons (receptor types DP and EP2) and primary afferent neurons (EP1, EP3, EP4 and IP). Acute and chronic peripheral inflammation, interleukins and spinal cord injury increase the expression of COX-2 and release of PGE(2) and PGI(2). By activating the cAMP and protein kinase A pathway, PGs enhance tetrodotoxin-resistant sodium currents, inhibit voltage-dependent potassium currents and increase voltage-dependent calcium inflow in nociceptive afferents. This decreases firing threshold, increases firing rate and induces release of excitatory amino acids, substance P, calcitonin gene-related peptide (CGRP) and nitric oxide. Conversely, glutamate, substance P and CGRP increase PG release. Prostaglandins also facilitate membrane currents and release of substance P and CGRP induced by low pH, bradykinin and capsaicin. All this should enhance elicitation and synaptic transfer of pain signals in the spinal cord. Direct administration of PGs to the spinal cord causes hyperalgesia and allodynia, and some studies have shown an association between induction of COX-2, increased PG release and enhanced nociception. NSAIDs diminish both basal and enhanced PG release in the spinal cord. Correspondingly, spinal application of NSAIDs generally diminishes neuronal and behavioral responses to acute nociceptive stimulation, and always attenuates behavioral responses to persistent nociception. Spinal application of specific COX-2 inhibitors sometimes diminishes behavioral responses to persistent nociception.