Immunohistochemical Expression of Cyclooxygenase-2 in Normal Kidneys

Progress in PET Imaging of Neuroinflammation Targeting COX-2 Enzyme

Neuroinflammation and cyclooxygenase-2 (COX-2) upregulation are associated with the pathogenesis of degenerative brain diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), epilepsy, and a response to traumatic brain injury (TBI) or stroke. COX-2 is also induced in acute pain, depression, schizophrenia, various cancers, arthritis and in acute allograft rejection. Positron emission tomography (PET) imaging allows for the direct measurement of in vivo COX-2 upregulation and thereby enables disease staging, therapy evaluation and aid quantifying target occupancy of novel nonsteroidal anti-inflammatory drugs or NSAIDs. Thus far, no clinically useful radioligand is established for monitoring COX-2 induction in brain diseases due to the delay in identifying qualified COX-2-selective inhibitors entering the brain. This review examines radiolabeled COX-2 inhibitors reported in the past decade and identifies the most promising radioligands for development as clinically useful PET radioligands. Among the radioligands reported so far, the three tracers that show potential for clinical translation are, [11CTMI], [11C]MC1 and [18F]MTP. These radioligands demonstrated BBB permeablity and in vivo binding to constitutive COX-2 in the brain or induced COX-2 during neuroinflammation.

Expression of neuronal nitric oxide synthase and renin in dysplastic kidneys of young dogs

Renin and neuronal nitric oxide synthase in the kidney control the renin-angiotensin and tubuloglomerular feedback systems. The present study investigated the expression of renin and neuronal nitric oxide synthase in the dysplastic kidneys of three young dogs. Renin-immunoreactivity, which occurs in the juxtaglomerular and tubular cells of dysplastic kidneys, did not differ from that in the normal kidneys of young dogs. Macula densa cells in the normal kidneys showed neuronal nitric oxide synthase -immunoreactivity, but those in the dysplastic kidneys showed no apparent signals. This observation may be correlated with the pathological mechanisms of renal failure in young dogs.

Radiosynthesis and Biological Evaluation of [18F]Triacoxib: A New Radiotracer for PET Imaging of COX-2

Inducible isozyme cyclooxygenase-2 (COX-2) is upregulated under acute and chronic inflammatory conditions, including cancer, wherein it promotes angiogenesis, tissue invasion, and resistance to apoptosis. Due to its high expression in various cancers, COX-2 has become an important biomarker for molecular imaging and therapy of cancer. Recently, our group applied in situ click chemistry for the identification of the highly potent and selective COX-2 inhibitor triacoxib. In this study, we present the radiosynthesis in vitro and in vivo radiopharmacological validation of [¹⁸F]triacoxib, a novel radiotracer for PET imaging of COX-2. Radiosynthesis of [¹⁸F]triacoxib was accomplished using copper-mediated late-stage radiofluorination chemistry. The radiosynthesis, including radio-HPLC purification, of [¹⁸F]triacoxib was accomplished within 90 min in decay-corrected radiochemical yields of 72% (n = 7) at molar activities exceeding 90 GBq/μmol. Cellular uptake and inhibition studies with [¹⁸F]triacoxib were carried out in COX-2 expressing HCA-7 cells. Cellular uptake of [¹⁸F]triacoxib in HCA-7 cells reached 25% radioactivity/mg protein after 60 min. Cellular uptake was reduced by 63% upon pretreatment with 0.1 mM celecoxib, and 90% of the radiotracer remained intact in vivo after 60 min p.i. in mice. [¹⁸F]Triacoxib was further evaluated in HCA-7 tumor-bearing mice using dynamic PET imaging, radiometabolite analysis, autoradiography, and immunohistochemistry. PET imaging revealed a favorable baseline radiotracer uptake in HCA-7 tumors (SUV_60min = 0.76 ± 0.02 (n = 4)), which could be blocked by 20% through i.p. pretreatment with 2 mg of celecoxib. Autoradiography and immunohistochemistry experiments further the confirmed blocking of COX-2 in vivo. [¹⁸F]Triacoxib, whose nonradioactive analogue was identified through in situ click chemistry, is a novel radiotracer for PET imaging of COX-2 in cancer. Despite a substantial amount of nonspecific uptake in vivo, [¹⁸F]triacoxib displayed specific binding to COX-2 in vivo and reinforced the feasibility of optimal structure selection by in situ click chemistry. It remains to be elucidated how this novel radiotracer would perform in first-in-human studies to detect COX-2 with PET.

GDNF enhances the anti-inflammatory effect of human adipose-derived mesenchymal stem cell-based therapy in renal interstitial fibrosis

Adipose-derived mesenchymal stem cells (AMSCs) are a type of adult stem cell from the mesoderm with the capacity to migrate and differentiate into other cell lineages. As a morphogenetic state of stem cells, glial-derived neurotrophic factor (GDNF) has been found to promote cell proliferation and differentiation of stem cells. The aims of our study were to investigate the biological activity of AMSCs and whether the GDNF gene can enhance the anti-inflammatory properties of stem cells. In this study, stable proliferative GDNF-overexpressing AMSC lines were successfully established and the AMSCs/GDNF-AMSCs were cocultured with macrophages (Mφ) derived from THP-1 cells in a transwell system. The mRNA expression levels of tumor necrosis factor-alpha (TNF-α), inducible nitric oxide synthase (iNOS), interleukin (IL)-10 and IL-4 were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). In addition, the expressions of CD163 and CD206, two markers of M2 macrophages, were detected with flow cytometric analysis. In animal experiments, AMSCs/GDNF-AMSCs (5 × 10⁵) were administered to unilateral ureteral obstruction (UUO) nude mice for 3 or 7 days. The expression levels of cyclooxygenase-2 (COX-2), IL-6, transforming growth factor β1 (TGF-β1) and α-Smooth muscle actin (α-SMA) were determined by Western blotting. Renal pathological changes of all groups were observed by hematoxylin and eosin (HE) and Masson staining. In conclusion, in vitro cultured AMSCs induced a shift in macrophage phenotype from the inflammatory (M1) phenotype to the reparative (M2) phenotype. In the UUO model, AMSC treatment was conducive to the recovery of renal function and interstitial fibrosis. Therefore, we determined that AMSC therapy could promote the phenotypic transformation of macrophages and reduce the progression of renal fibrosis by suppressing inflammation. GDNF could enhance the anti-inflammatory effect of AMSCs.

Avaliação de anti-inflamatórios não esteroidais no tratamento da dor de ovinos submetidos à implantação de cânula ruminal e orquiectomia

RESUMO O presente trabalho objetivou comparar o efeito do flunixin meglumine, cetoprofeno e meloxicam no tratamento da dor pós-operatória de ovinos submetidos à implantação de cânula ruminal e orquiectomia. Foram utilizados 32 ovinos, machos, pesando em média 35,5±3,5kg, distribuídos em três grupos: GFlu (flunixin meglumine 1,1mg/kg i.v.), GCet (cetoprofeno 3,0mg/kg i.v.) e GMel (meloxicam 0,5mg/kg i.v.). Exame clínico e coletas de sangue foram realizados no M0 (pré-avaliação), M1 (10 minutos após a pré-avaliação), M2 (início da sutura para fixação da cânula ruminal), M3 (logo após o término da cirurgia) e em duas, 12, 23, 25, 48 e 72 horas após a cirurgia (M2h, M12h, M23h, M25h, M48h e M72h), quando foram avaliados cortisol, glicose, proteína total, albumina, γ-glutamiltransferase (GGT), aspartato aminotransferase (AST), creatina quinase (CK), ureia, creatinina e hemograma. Nos M2h, M12h, M23h, M25h e M48h, foi realizada avaliação comportamental. O GFlu apresentou maior concentração de cortisol no M12h e no M48h e maior escore de dor na fístula e no testículo no M12h, quando comparado ao GMel. Os animais do GCet apresentaram menor interação com outros membros da baia no M23h. A ação analgésica do meloxicam foi maior em animais submetidos à implantação de cânula ruminal e orquiectomia, quando comparado ao flunixin meglumine e ao cetoprofeno.

Studies of postpartum mammary gland involution reveal novel pro-metastatic mechanisms

Postpartum involution is the process by which the lactating mammary gland returns to the pre-pregnant state after weaning. Expression of tumor-promotional collagen, upregulation of matrix metalloproteinases, infiltration of M2 macrophages, and remodeling of blood and lymphatic vasculature are all characteristics shared by the involuting mammary gland and breast tumor microenvironment. The tumor promotional nature of the involuting mammary gland is perhaps best evidenced by cases of postpartum breast cancer (PPBC), or those cases diagnosed within 10 years of most recent childbirth. Women with PPBC experience more aggressive disease and higher risk of metastasis than nulliparous patients and those diagnosed outside the postpartum window. Semaphorin 7a (SEMA7A), cyclooxygenase-2 (COX-2), and collagen are all expressed in the involuting mammary gland and, together, predict for decreased metastasis free survival in breast cancer. Studies investigating the role of these proteins in involution have been important for understanding their contributions to PPBC. Postpartum involution thus represents a valuable model for the identification of novel molecular drivers of PPBC and classical cancer hallmarks. In this review, we will highlight the similarities between involution and cancer in the mammary gland, and further define the contribution of SEMA7A/COX-2/collagen interplay to postpartum involution and breast tumor progression and metastasis.

The role of aspirin in colorectal cancer chemoprevention

Considerable interest has emerged over the last decade regarding the role of aspirin in prevention of colorectal cancer. This disease is one of the commonest cancers in the Western World, therefore, the existence of a simple "everyday" agent, which could have the ability to prevent the disease, represents an invaluable opportunity clinicians may be able to exploit. Evidence from case-control and cohort studies, and recent updates of randomised controlled trials have been very encouraging-indicating benefit from long term use of aspirin at low dose. Possible mechanisms of chemoprevention include inhibition of the cyclooxygenase (COX) pathway, or COX-independent mechanisms, for example, the PIK3CA pathway, or therapy-induced senescence of cancer cells. The most serious side effect of prolonged aspirin treatment is haemorrhage, especially from the GI tract. This is likely to be less of a problem with chemoprevention at lower doses. One also needs to consider the impact if aspirin resistance, an increasingly recognised clinical entity.

Exploring the Effects of Omega-3 and Omega-6 Fatty Acids on Allergy Using a HEK-Blue Cell Line

BACKGROUND

Allergic reactions can result in life-threatening situations resulting in high economic costs and morbidity. Therefore, more effective reagents are needed for allergy treatment. A causal relationship has been suggested to exist between the intake of omega-3/6 fatty acids, such as docosahexanoic acid (DHA), eicosapentanoic acid (EPA), docosapentanoic acid (DPA) and arachidonic acid (AA), and atopic individuals suffering from allergies. In allergic cascades, the hallmark cytokine IL-4 bind to IL-4 receptor (IL-4R) and IL-13 binds to IL-13 receptor (IL-13R), this activates the STAT6 phosphorylation pathway leading to gene activation of allergen-specific IgE antibody production by B cells. The overall aim of this study was to characterize omega-3/6 fatty acids and their effects on STAT6 signaling pathway that results in IgE production in allergic individuals.

METHODS

The fatty acids were tested in vitro with a HEK-Blue IL-4/IL-13 reporter cell line model, transfected with a reporter gene that produces an enzyme, secreted embryonic alkaline phosphatase (SEAP). SEAP acts as a substitute to IgE when cells are stimulated with bioactive cytokines IL-4 and/or IL-13.

RESULTS

We have successfully used DHA, EPA and DPA in our studies that demonstrated a decrease in SEAP secretion, as opposed to an increase in SEAP secretion with AA treatment. A statistical Student's t-test revealed the significance of the results, confirming our initial hypothesis.

CONCLUSION

We have successfully identified and characterised DHA, EPA, DPA and AA in our allergy model. While AA was a potent stimulator, DHA, EPA and DPA were potential inhibitors of IL-4R/IL-13R signalling, which regulates the STAT6 induced pathway in allergic cascades. Such findings are significant in the future design of dietary therapeutics for the treatment of allergies.

NSAIDs Alter Phosphorylated Forms of AQP2 in the Inner Medullary Tip

Vasopressin increases urine concentration through activation of aquaporin-2 (AQP2) in the collecting duct. Nonsteroidal anti-inflammatory drugs (NSAIDs) block prostaglandin E2 synthesis, and may suppress AQP2 producing a urine concentrating defect. There are four serines in AQP2 that are phosphorylated by vasopressin. To determine if chronic use of NSAIDs changes AQP2's phosphorylation at any of these residues, the effects of a non-selective NSAID, ibuprofen, and a COX-2-selective NSAID, meloxicam, were investigated. Daily ibuprofen or meloxicam increased the urine output and decreased the urine osmolality significantly by days 7 through 14. Concomitantly, meloxicam significantly reduced total AQP2 protein abundance in inner medulla (IM) tip to 64% of control and base to 63%, respectively. Ibuprofen significantly decreased total AQP2 in IM tip to 70% of control, with no change in base. Meloxicam significantly increased the ratios of p256-AQP2 and p261-AQP2 to total AQP2 in IM tip (to 44% and 40%, respectively). Ibuprofen increased the ratio of p256-AQP2 to total AQP2 in IM tip but did not affect p261-AQP2/total AQP2 in tip or base. Both ibuprofen and meloxicam increased p264-AQP2 and p269-AQP2 ratios in both tip and base. Ibuprofen increased UT-A1 levels in IM tip, but not in base. We conclude that NSAIDs reduce AQP2 abundance, contributing to decreased urine concentrating ability. They also increase some phosphorylated forms of AQP2. These changes may partially compensate for the decrease in AQP2 abundance, thereby lessening the decrease in urine osmolality.

Cyclooxygenase metabolites in the kidney

In the mammalian kidney, prostaglandins (PGs) are important mediators of physiologic processes, including modulation of vascular tone and salt and water. PGs arise from enzymatic metabolism of free arachidonic acid (AA), which is cleaved from membrane phospholipids by phospholipase A2 activity. The cyclooxygenase (COX) enzyme system is a major pathway for metabolism of AA in the kidney. COX are the enzymes responsible for the initial conversion of AA to PGG2 and subsequently to PGH2, which serves as the precursor for subsequent metabolism by PG and thromboxane synthases. In addition to high levels of expression of the "constitutive" rate-limiting enzyme responsible for prostanoid production, COX-1, the "inducible" isoform of cyclooxygenase, COX-2, is also constitutively expressed in the kidney and is highly regulated in response to alterations in intravascular volume. PGs and thromboxane A2 exert their biological functions predominantly through activation of specific 7-transmembrane G-protein-coupled receptors. COX metabolites have been shown to exert important physiologic functions in maintenance of renal blood flow, mediation of renin release and regulation of sodium excretion. In addition to physiologic regulation of prostanoid production in the kidney, increases in prostanoid production are also seen in a variety of inflammatory renal injuries, and COX metabolites may serve as mediators of inflammatory injury in renal disease.

Beneficial Effect of 7-O-Galloyl-D-sedoheptulose, a Polyphenol Isolated from Corni Fructus, against Diabetes-Induced Alterations in Kidney and Adipose Tissue of Type 2 Diabetic db/db Mice

Traditional medicines are being focused on as possible treatments for diabetes and its complications because of their negligible toxic and/or side effects. In line with this, our group has reported that Corni Fructus, a traditional medicine considered exhibiting beneficial effects on liver and kidney functions, possessed an antidiabetic effect via ameliorating glucose-mediated metabolic disorders. To add to these findings, we screened the iridoid glycoside fraction containing morroniside and loganin, and low molecular weight polyphenol fraction containing 7-O-galloyl-d-sedoheptulose (GS) from Corni Fructus. To our knowledge, GS is a compound only detected in Corni Fructus, and its biological activity has been poorly understood until now. For these reasons, we examined whether GS has an ameliorative effect on diabetic changes using type 2 diabetic db/db mice. Our findings suggest that GS has a beneficial effect on the pathological state of the serum, kidney, and adipose tissue related to diabetic damage.

LC-MS/MS confirms that COX-1 drives vascular prostacyclin whilst gene expression pattern reveals non-vascular sites of COX-2 expression

There are two schools of thought regarding the cyclooxygenase (COX) isoform active in the vasculature. Using urinary prostacyclin markers some groups have proposed that vascular COX-2 drives prostacyclin release. In contrast, we and others have found that COX-1, not COX-2, is responsible for vascular prostacyclin production. Our experiments have relied on immunoassays to detect the prostacyclin breakdown product, 6-keto-PGF_1α and antibodies to detect COX-2 protein. Whilst these are standard approaches, used by many laboratories, antibody-based techniques are inherently indirect and have been criticized as limiting the conclusions that can be drawn. To address this question, we measured production of prostanoids, including 6-keto-PGF_1α, by isolated vessels and in the circulation in vivo using liquid chromatography tandem mass spectrometry and found values essentially identical to those obtained by immunoassay. In addition, we determined expression from the Cox2 gene using a knockin reporter mouse in which luciferase activity reflects Cox2 gene expression. Using this we confirm the aorta to be essentially devoid of Cox2 driven expression. In contrast, thymus, renal medulla, and regions of the brain and gut expressed substantial levels of luciferase activity, which correlated well with COX-2-dependent prostanoid production. These data are consistent with the conclusion that COX-1 drives vascular prostacyclin release and puts the sparse expression of Cox2 in the vasculature in the context of the rest of the body. In doing so, we have identified the thymus, gut, brain and other tissues as target organs for consideration in developing a new understanding of how COX-2 protects the cardiovascular system.

Cyclooxygenase (COX) Inhibitors and the Newborn Kidney

This review summarizes our current understanding of the role of cyclo-oxygenase inhibitors (COXI) in influencing the structural development as well as the function of the developing kidney. COXI administered either during pregnancy or after birth can influence kidney development including nephronogenesis, and can decrease renal perfusion and ultrafiltration potentially leading to acute kidney injury in the newborn period. To date, which COX isoform (COX-1 or COX-2) plays a more important role in during fetal development and influences kidney function early in life is not known, though evidence points to a predominant role for COX-2. Clinical implications of the use of COXI in pregnancy and in the newborn infant are also evaluated herein, with specific reference to the potential effects of COXI on nephronogenesis as well as newborn kidney function.

7-O-Galloyl-d-sedoheptulose ameliorates renal damage triggered by reactive oxygen species-sensitive pathway of inflammation and apoptosis

Objectives

This study was carried out to verify the preventive effects of 7-O-galloyl-d-sedoheptulose (GS), a phenolic compound isolated from Corni Fructus, underlying diabetic renal damage in type 2 diabetes.

Methods

GS was orally administered to db/db mice at doses of 20 and 100 mg/kg body weight per day for six weeks, and its effects were compared with those of the vehicle in db/db and m/m mice.

Key findings

In the serum and kidney, biochemical factors and expression of protein related to nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, apoptosis and inflammation were examined. GS treatment attenuated serum and renal oxidative stress through reduction of reactive oxygen species and lipid peroxidation and increase in the ratio of glutathione and its oxidised form. Importantly, GS reduced renal protein expression of Nox-4 and p22phox (one of the subunits of NADPH oxidase), pro-apoptotic factors (such as Bax and cytochrome c) and nuclear factor-kappa B-targeting pro-inflammatory inducible nitric oxide synthase and cyclooxygenase-2.

Conclusions

These renoprotective effects of GS were achieved through attenuation of diabetes-induced oxidative stress and its sensitive protein expression associated with inflammation and apoptosis in db/db mice.

Expression of cyclooxygenase-1 (COX-1) and COX-2 in human male gametes from normal patients, and those with varicocele and diabetes: a potential molecular marker for diagnosing male infertility disorders

Rising rates of varicocele and diabetes mellitus (DM) pose a significant problem to human fertility. Recent studies have pointed out the impact of cyclooxygenase (COX) in the regulation of testicular function and male fertility. Prominent COX-2 expression has been described recently in the testes of infertile patients, but little is known about the role and identity of COX isoforms in human sperm under certain disease states such as varicocele and DM. We therefore examined the expression profile and ultrastructural localization of COX-1 and COX-2 concomitantly in semen samples from healthy donors, and patients with varicocele and DM. Using Western blotting assay, 'varicocele' and 'diabetic' sperm showed enhanced COX isoforms expression with respect to the 'healthy' sperm. Immunogold labeling revealed human sperm anatomical regions containing COX-1 and COX-2, confirming their increased expression in pathological samples. Our data demonstrate that both COX isoforms are upregulated in the spermatozoa of varicocele and diabetic patients, suggesting the harmful effect of the diseases also at the sperm molecular level, going beyond the abnormal morphology described to date. In conclusion, COX enzymes may possess a biological relevance in the pathogenesis and/or maintenance of male factor infertility associated with varicocele and DM, and may be considered additional molecular markers for the diagnosis of male infertility disorders.

Immunohistochemical identification of kidney nephron segments in the dog, rat, mouse, and cynomolgus monkey

Kidney is a major target organ in preclinical studies. In recent years, intense research has been undertaken to characterize novel renal toxicity biomarkers. In this context, we studied nephron segment specific antibodies against aquaporin-1 (AQP-1), α-glutathione-S-transferase (alpha-GST), Tamm-Horsfall protein (TH), calbindin-D(28K) (CalD), and aquaporin-2 (AQP-2), using an immunoperoxidase method on formalin-fixed paraffin-embedded kidney tissues of dogs, rats, mice, and Cynomolgus monkeys. AQP-1 was specific for proximal tubules and thin descending limbs of Henle's loops and AQP-2 for connecting and collecting ducts in dogs, rats, mice, and Cynomolgus monkeys. Alpha-GST stained the straight part of proximal tubules in dogs and proximal convoluted tubule and straight part of proximal tubules in rats. TH was specific for thick ascending limbs of Henle's loops in mice, rats, dogs, and Cynomolgus monkeys and stained additionally scattered cells in cortical connecting/collecting ducts of dogs. CalD was found in distal convoluted tubules and cortical connecting and collecting ducts of dogs, rats, and mice and in distal convoluted tubules, connecting ducts, and cortical and medullary collecting ducts of Cynomolgus monkey. This panel of antibodies may be a helpful tool to identify renal tubules by light microscopy in preclinical studies and to validate new biomarkers of renal toxicity.

Podocyte COX-2 exacerbates diabetic nephropathy by increasing podocyte (pro)renin receptor expression

Diabetic nephropathy (DN) increases podocyte cyclooxygenase-2 (COX-2) expression, and COX-2 inhibition reduces proteinuria and glomerular injury in animal models of diabetes. To investigate the role of podocyte COX-2 in development of diabetic nephropathy, we employed a streptozotocin model of diabetic mellitus in wild-type and transgenic mice expressing COX-2 selectively in podocytes. Progressive albuminuria developed only in diabetic COX-2 transgenic mice despite hyperglycemia, BP, and GFR being similar to those in wild-type mice. Transgenic mice also manifested significant foot-process effacement, moderate mesangial expansion, and segmental thickening of the glomerular basement membrane. In cultured podocytes overexpressing COX-2, high glucose induced cell injury and increased both expression of the pro(renin) receptor and activation of the renin-angiotensin system. Downregulation of the (pro)renin receptor attenuated the injury induced by high glucose. In vivo, podocyte pro(renin) receptor expression increased in diabetic COX-2-transgenic mice, and treatment with a COX-2 inhibitor abrogated the upregulation of (pro)renin receptor and reduced albuminuria, foot-process effacement, and mesangial matrix expansion. In summary, these results demonstrate that increased expression of podocyte COX-2 predisposes to diabetic glomerular injury and that the (pro)renin receptor may be one mediator for this increased susceptibility to injury.

Upregulation of cyclooxygenase-2 expression in porcine macula densa with chronic nitric oxide synthase inhibition

The objective of this study was to investigate the effects of chronic inhibition of nitric oxide synthase (NOS) on cyclooxygenase-2 (COX-2) expression in the macula densa (MD) of swine, as well as the effects on expression of related proteins. Adult female Yucatan swine were given either tap water (control, n = 6) or water with N (G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/liter, n = 5) for a minimum of 30 days. Duplicate samples of kidney were fixed or snap frozen. There was a significant (P = .0082) upregulation of COX-2 mRNA expression in the MD of L-NAME, as well as an apparent increase in COX-2 protein. Plasma renin activity also increased with L-NAME treatment (control, 0.34 ± 0.08 ng/ml; L-NAME, 1.26 ± 0.03 ng/ml; P = .00000003). There were no differences between groups in expression of either inducible NOS or renin protein or in serum electrolyte concentrations. In conclusion, with chronic inhibition of NOS, COX-2 in MD is upregulated, perhaps to compensate for loss of nitric oxide. Increases in COX-2 products may counteract renal arteriolar constriction and sustain renin release.

The COX-2/PGE2 pathway: key roles in the hallmarks of cancer and adaptation to the tumour microenvironment

It is widely accepted that alterations to cyclooxygenase-2 (COX-2) expression and the abundance of its enzymatic product prostaglandin E(2) (PGE(2)) have key roles in influencing the development of colorectal cancer. Deregulation of the COX-2/PGE(2) pathway appears to affect colorectal tumorigenesis via a number of distinct mechanisms: promoting tumour maintenance and progression, encouraging metastatic spread, and perhaps even participating in tumour initiation. Here, we review the role of COX-2/PGE(2) signalling in colorectal tumorigenesis and highlight its ability to influence the hallmarks of cancer--attributes defined by Hanahan and Weinberg as being requisite for tumorigenesis. In addition, we consider components of the COX-prostaglandin pathway emerging as important regulators of tumorigenesis; namely, the prostanoid (EP) receptors, 15-hydroxyprostaglandin dehydrogenase and the prostaglandin transporter. Finally, based on recent findings, we propose a model for the cellular adaptation to the hypoxic tumour microenvironment that encompasses the interplay between COX-2, hypoxia-inducible factor 1 and dynamic switches in beta-catenin function that fine-tune signalling networks to meet the ever-changing demands of a tumour.

Renal effects of prostaglandins and cyclooxygenase-2 inhibitors

Prostaglandins (PGs) with best-defined renal functions are PGE₂ and prostacyclin (PGI₂). These vasodilatory PGs increase renal blood flow and glomerular filtration rate under conditions associated with decreased actual or effective circulating volume, resulting in greater tubular flow and secretion of potassium. Under conditions of decreased renal perfusion, the production of renal PGs serves as an important compensatory mechanism. PGI₂ (and possibly PGE₂) increases potassium secretion mainly by stimulating secretion of renin and activating the renin-angiotensin system, which leads to increased secretion of aldosterone. In addition, PGE₂ is involved in the regulation of sodium and water reabsorption and acts as a counterregulatory factor under conditions of increased sodium reabsorption. PGE₂ decreases sodium reabsorption at the thick ascending limb of the loop of Henle probably via inhibition of the Na⁺-K⁺-2Cl^- cotransporter type 2 (NKCC2). Cyclooxygenase inhibitors may enhance urinary concentrating ability in part through effects to upregulate NKCC2 in the thick ascending limb of Henle's loop and aquaporin-2 in the collecting duct. Thus, they may be useful to treat Bartter's syndrome and nephrogenic diabetes insipidus.

COX-2 and the kidney

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of pain and inflammation. Nonselective NSAIDs inhibit both cyclooxygenase (COX)-1 and COX-2. Nephrotoxicity of nonselective NSAIDs has been well documented. The effects of selective COX-2 inhibitors on renal function and blood pressure are attracting increasing attention. In the kidney, COX-2 is constitutively expressed and is highly regulated in response to alterations in intravascular volume. COX-2 metabolites have been implicated in the mediation of renin release, regulation of sodium excretion, and maintenance of renal blood flow. Similar to nonselective NSAIDs, inhibition of COX-2 may cause edema and modest elevations in blood pressure in a minority of subjects. COX-2 inhibitors may also exacerbate preexisting hypertension or interfere with other antihypertensive drugs. Occasional acute renal failure has also been reported. Caution should be taken when COX-2 inhibitors are prescribed, especially in high-risk patients (including elderly patients and patients with volume depletion).

Mediators of PGE2 synthesis and signalling downstream of COX-2 represent potential targets for the prevention/treatment of colorectal cancer

Colorectal cancer is a major cause of mortality and whilst up to 80% of sporadic colorectal tumours are considered preventable, trends toward increasing obesity suggest the potential for a further increase in its worldwide incidence. Novel methods of colorectal cancer prevention and therapy are therefore of considerable importance. Non-steroidal anti-inflammatory drugs (NSAIDs) are chemopreventive against colorectal cancer, mainly through their inhibitory effects on the cyclooxygenase isoform COX-2. COX enzymes represent the committed step in prostaglandin biosynthesis and it is predominantly increased COX-2-mediated prostaglandin-E2 (PGE2) production that has a strong association with colorectal neoplasia, by promoting cell survival, cell growth, migration, invasion and angiogenesis. COX-1 and COX-2 inhibition by traditional NSAIDs (for example, aspirin) although chemopreventive have some side effects due to the role of COX-1 in maintaining the integrity of the gastric mucosa. Interestingly, the use of COX-2 selective NSAIDs has also shown promise in the prevention/treatment of colorectal cancer while having a reduced impact on the gastric mucosa. However, the prolonged use of high dose COX-2 selective inhibitors is associated with a risk of cardiovascular side effects. Whilst COX-2 inhibitors may still represent viable adjuvants to current colorectal cancer therapy, there is an urgent need to further our understanding of the downstream mechanisms by which PGE2 promotes tumorigenesis and hence identify safer, more effective strategies for the prevention of colorectal cancer. In particular, PGE2 synthases and E-prostanoid receptors (EP1-4) have recently attracted considerable interest in this area. It is hoped that at the appropriate stage, selective (and possibly combinatorial) inhibition of the synthesis and signalling of those prostaglandins most highly associated with colorectal tumorigenesis, such as PGE2, may have advantages over COX-2 selective inhibition and therefore represent more suitable targets for long-term chemoprevention. Furthermore, as COX-2 is found to be overexpressed in cancers such as breast, gastric, lung and pancreatic, these investigations may also have broad implications for the prevention/treatment of a number of other malignancies.

Expression of cyclooxygenase-1 and cyclooxygenase-2 in human renal allograft rejection - a prospective study

Cyclooxygenases (COX) are known to be involved in inflammatory kidney diseases. However, there are no data available about the expression of COX-1 and only preliminary reports about the expression of COX-2 in biopsies of patients undergoing acute renal allograft rejection. We conducted this prospective study to analyze the expression, distribution, and cellular localization of COX-1 and -2 and thus to elucidate the role of COX in human kidney transplantation. One hundred forty-four biopsies were included from patients without rejection and unaltered morphology (n = 60), with acute interstitial rejection (n = 7), with acute vascular rejection (n = 21), with chronic allograft nephropathy (n = 16), without rejection but with various other lesions (n = 40). COX-1 and -2 expression was localized in each biopsy by immunohistochemistry. We found a highly significant up-regulation of COX-1 in vessels and in infiltrating interstitial cells of patients with acute allograft rejection compared with biopsies with well-preserved tissue. Also, COX-2 expression was significantly elevated in infiltrating interstitial cells of biopsies with acute rejection. This is the first prospective study demonstrating a significant induction of both COX-1 and -2 in human allograft biopsies with acute rejection after renal transplantation.

Prospects in NSAID-derived chemoprevention of colorectal cancer

There is strong evidence for an important role for increased COX (cyclo-oxygenase)-2 expression and PG (prostaglandin) E2 production in colorectal tumorigenesis. PGE(2) acts through four E-prostanoid receptors (EP1-4). COX-2 has therefore become a target for the potential chemoprevention and therapy of colorectal cancer. However, any therapeutic/preventive strategy has the potential to have an impact on physiological processes and hence result in side effects. General COX (COX-1 and -2) inhibition by traditional NSAIDs (non-steroidal anti-inflammatory drugs), such as aspirin, although chemopreventive, has some side effects, as do some conventional COX-2-selective NSAIDs. As PGE2 is thought to be the major PG species responsible for promoting colorectal tumorigenesis, research is being directed to a number of protein targets downstream of COX-2 that might allow the selective inhibition of the tumour-promoting activities of PGE2, while minimizing the associated adverse events. The PGE synthases and E-prostanoid receptors (EP1-4) have therefore recently attracted considerable interest as potential novel targets for the prevention/therapy of colorectal cancer. Selective (and possibly combinatorial) inhibition of the synthesis and signalling of those PGs most highly associated with colorectal tumorigenesis may have some advantages over COX-2-selective inhibitors.

Hemangioma versus vascular malformation: presence of nerve bundle is a diagnostic clue for vascular malformation

CONTEXT

Arteriovenous vascular malformations and hemangiomas are benign vascular lesions that are difficult to distinguish from one another clinically. Also, they may be confused with each other at histopathology. Therefore, histochemical stains for the presence of an artery are frequently used to distinguish between the two.

OBJECTIVE

Because it is clinically relevant to differentiate between arteriovenous vascular malformations and hemangiomas, this study was carried out to explore additional diagnostic clues that may help in the diagnosis and differentiation of these lesions.

DESIGN

A total of 167 cases of benign extracranial vascular lesions were retrieved from the anatomic pathology file of our institution. These comprised 66 cases diagnosed as arteriovenous vascular malformations and 101 cases previously diagnosed as hemangiomas. The hematoxylin-eosin-stained glass slides were reviewed, Movat pentichrome histochemical stain was used to identify elastic vessels (arteries/arterioles), and S100 immunostain was used to identify nerves within these vascular lesions. For immunohistochemistry, the avidin-biotin detection method was used.

RESULTS

With Movat stain, the presence of thick-walled elastic arteries was detected in 12 of the 101 cases previously diagnosed as hemangiomas, and these cases were therefore reclassified as vascular malformations. Using the same criterion, 2 of the 66 cases originally diagnosed as arteriovenous vascular malformations were reclassified as hemangiomas because they lacked arterial structures. Thus, with this strict criterion, we ended up with 91 cases of hemangiomas and 76 cases of arteriovenous vascular malformations. Intralesional nerves were identified in 91% (69/76) of cases of arteriovenous vascular malformations, including all the 12 arteriovenous vascular malformations previously diagnosed as hemangiomas. In contrast, no intralesional nerve was detected in any of the 91 hemangiomas.

CONCLUSIONS

These results show that nerve bundles are consistently present in vascular malformations and absent in hemangiomas and so can be used as a diagnostic clue to differentiate between these lesions. Also, in addition to describing a previously unreported component of vascular malformations, these data further confirm the hamartomatous nature of these lesions.

Hypertonic Induction of COX-2 in Collecting Duct Cells by Reactive Oxygen Species of Mitochondrial Origin

Our previous studies have documented MAPK mediation of the hypertonicity-induced stimulation of COX-2 expression in cultured renal medullary epithelial cells. The present study extends this observation by examining the role of reactive oxygen species (ROSs). ROS levels, determined using dichlorodihydrofluorescence diacetate and cytochrome c, were rapidly and significantly increased following exposure of mIMCD-K2 cells to media made hypertonic by adding NaCl. Hypertonic treatment (550 mosmol/kg) for 16 h induced a 5.6-fold increase in COX-2 protein levels and comparable increases in prostaglandin E(2) release, both of which were completely abolished by the NADPH oxidase inhibitor diphenyleneiodonium (25-50 microM). The general antioxidant N-acetyl-l-cysteine (6 mM), and the superoxide dismutase mimetic TEMPO (2.0 mm) reduced COX-2 levels by 75.6 and 79.8%, respectively. Exposure of mIMCD-K2 cells to exogenous O(2)(-.) generated by the xanthine/xanthine oxidase system mimicked the effect of hypertonicity on COX-2 expression and prostaglandin E(2) release. The increases in phosphorylation of ERK1/2 and p38 were detected 20 min following the hypertonic treatment and were both prevented by N-acetyl-l-cysteine. The increases in ROSs in response to hypertonic treatment were completely blocked by any one of the mitochondrial inhibitors tested, such as rotenone, thenoyltrifluoroacetone, or carbonyl cyanide m-chlorophenylhydrazone, associated with remarkable inhibition of COX-2 expression. In contrast, the increases in ROSs were not significantly altered in IMCD cells deficient in either gp91(phox) or p47(phox), nor were the increases in COX-2 expression. We conclude that ROSs derived from mitochondria, but not NADPH oxidase, mediate the hypertonicity-induced phosphorylation of MAPK and the stimulation of COX-2 expression.

Prostacyclin signaling in the kidney: implications for health and disease

The balance between vasodilator and vasoconstrictor pathways is key to the maintenance of homeostasis and the outcome of disease. In the kidney, prostaglandins (PGs) uphold this balance and regulate renal function: hemodynamics, renin secretion, growth responses, tubular transport processes, and cell fate. With the advent of cyclooxygenase (COX)-2-selective inhibitors, targeted deletions in mice (COX knockouts, PG receptor knockouts), and the discovery of intracrine signaling options for PGs (peroxisome proliferator-activated receptors and perinuclear PGE2receptors: EP1,3,4), many advances have been made in the study of arachidonic acid metabolites. Although prostacyclin (PGI2) is a major product of the COX pathway, there is very little emphasis on its importance to the kidney. This review will discuss PGI2biology and its relevance to different aspects of renal disease (growth, fibrosis, apoptosis), highlighting the most significant research from the past decade of PGI2literature, what we have learned from other organ systems, while stressing the significance of cross talk between various PGI2signaling pathways and its implications for renal health and disease.

Is COX-2 a perpetrator or a protector? Selective COX-2 inhibitors remain controversial

COX-2(cyclooxygenase-2) has sparked a surge in pharmaceutical interest since its discovery at the beginning of the 1990s. Several COX-2 selective inhibitors that avoid gastrointestinal side effects have been successfully launched into the market in recent years. The first selective COX-2 inhibitor, celecoxib, entered the market in December 1998 [corrected] However, there are a few organs that physiologically and functionally express COX-2, particularly the glomeruli of the kidney and the cortex of the brain. Inhibition of COX-2 expression in these organs possibly causes heart attack and stroke in long-term COX-2 inhibitor users. Recently, a USA Food and Drug Agency (FDA) advisory panel re-evaluated COX-2 inhibitors and unanimously concluded that the entire class of COX-2 inhibitors increase the risk of cardiovascular problems. Thus the use of COX-2 inhibitors is still controversial, and there is a challenge for not only pharmacologists, but also the pharmaceutical industry, to develop improved painkilling and anti-inflammatory drugs. This may involve exploring a new generation of COX-2 inhibitors with different inhibitory mechanisms through computer-aided design, screening different sources of inhibitors with lower selectivity, or seeking completely new targets. Synthetic COX-2 inhibitors have high selectivity and the advantage of irreversible inhibition, whereas naturally derived COX-2 inhibitors have lower selectivity and fewer side effects, with the medical effects in general not being as striking as those achieved using synthetic inhibitors. This review discusses the mechanism of COX-2 inhibitor therapy and a possible new way of exploration in the development of anti-inflammatory, analgetic, and antipyretic drugs.