Chemical and Biological Studies on Indomethacin, Sulindac and their Analogs

Direct Impairment of the Endothelial Function by Acute Indoxyl Sulfate through Declined Nitric Oxide and Not Endothelium-Derived Hyperpolarizing Factor or Vasodilator Prostaglandins in the Rat Superior Mesenteric Artery

Upon stimulation, endothelial cells release various factors to regulate the vascular tone. In particular, vasorelaxing factors, called endothelium-derived relaxing factors (EDRFs), are altered in the production and/or release, as well as their signaling every vessel and under pathophysiological states, including cardiovascular, kidney, and metabolic diseases. Although indoxyl sulfate is known as a protein-bound uremic toxin and circulating levels are elevated in the impaired kidney functions, direct impact on the vascular function, especially EDRF's signaling, remains unclear. In this study, we hypothesize that acute exposure to indoxyl sulfate could alter vascular relaxation in the rat superior mesenteric artery. Accordingly, we measured acetylcholine (ACh)-induced endothelium-dependent relaxation in the absence and presence of several inhibitors to divide into each EDRF, including nitric oxide (NO), vasodilator prostaglandins (PGs), and endothelium-derived hyperpolarizing factor (EDHF). Indoxyl sulfate reduced the sensitivity to ACh but not sodium nitroprusside. Under cyclooxygenase (COX) inhibition or inhibitions of COX plus source of EDHF, such as small (SK_Ca)- and intermediate (IK_Ca)-conductance calcium-activated K⁺ channels, the decreased sensitivity to ACh in indoxyl sulfate exposed vessel was still preserved. However, under inhibition of NO synthase (NOS) or inhibitions of NOS and COX, the difference of sensitivity to ACh between vehicle and indoxyl sulfate was eliminated. These findings indicated that acute exposure of indoxyl sulfate in the rat superior mesenteric artery specifically explicitly impaired NO signaling but not EDHF or vasodilator PGs.

Activation of protein kinase G Increases the expression of p21CIP1, p27KIP1, and histidine triad protein 1 through Sp1

The anticancer role of cyclic guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase G (PKG) has become of considerable interest, but the underlying mechanisms are not fully established. In this study, we examined the effects of activation of PKG on the expression of three tumor suppressor proteins in human SW480 colon cancer cells. Our results revealed that treatment with cell permeable cGMP derivatives, or the cGMP phosphodiesterase inhibitor sulindac sulfone (exisulind, aptosyn, hereafter called exisulind) led to increased expression of the tumor suppressor proteins p21(CIP1), p27(KIP1), and Histidine triad protein 1 (HINT1), and their corresponding mRNAs. Overexpression of PKG Ibeta also caused increased expression of the p21(CIP1), p27(KIP1), and HINT1 proteins. Both the p21(CIP1) and p27(KIP1) promoters contain Sp1 binding sites and they were activated by PKG in luciferase reporter assays. Specific Sp1 sites in the p21 and p27 promoters were sufficient to mediate PKG-induced luciferase reporter activity, suggesting an interaction between Sp1 and PKG. Indeed, we found that PKG can phosphorylate Sp1 on serine residue(s) and this resulted in transcriptional activation of Sp1. Knockdown of Sp1 expression with siRNA inhibited the increased expression of p21(CIP1), p27(KIP1), and HINT1 induced by the cGMP derivative 8-pCPT-cGMP in SW480 cells. These novel effects of PKG activation on the expression of three tumor suppressor genes may explain, at least in part, the anticancer effects of activation of PKG. They also provide a rationale for further developing activators of PKG for the prevention and treatment of cancer.

Prodrug strategies to overcome poor water solubility

Drug design in recent years has attempted to explore new chemical spaces resulting in more complex, larger molecular weight molecules, often with limited water solubility. To deliver molecules with these properties, pharmaceutical scientists have explored many different techniques. An older but time-tested strategy is the design of bioreversible, more water-soluble derivatives of the problematic molecule, or prodrugs. This review explores the use of prodrugs to effect improved oral and parenteral delivery of poorly water-soluble problematic drugs, using both marketed as well as investigational prodrugs as examples. Prodrug interventions should be considered early in the drug discovery paradigm rather than as a technique of last resort. Their importance is supported by the increasing percentage of approved new drug entities that are, in fact, prodrugs.

Desmethyl derivatives of indomethacin and sulindac as probes for cyclooxygenase-dependent biology

Cyclooxygenases (COX) have been implicated in the etiology of a number of diseases, but defining the precise contribution of COXs to these diseases is challenging. Potent COX inhibitors exist, but they display off-target effects. 2'-Desmethyl derivatives of indomethacin and sulindac sulfide were synthesized that demonstrated reduced COX inhibitory activity but were inducers of peroxisome proliferator-activated receptor gamma-dependent transcription, adipocyte differentiation, or apoptosis of colon cancer cell lines. 2'-Desmethylindomethacin demonstrated gastrointestinal toxicity lower than that of indomethacin in C57BL6 mice, highlighting the importance of COX activity in maintaining gastrointestinal homeostasis and establishing that COX inhibition contributes to gastrointestinal toxicity by nonsteroidal antiinflammatory drugs. These compounds serve as useful probes of COX-dependent biology and may represent leads for antidiabetic and anticancer drugs.

Discovery of potent CRTh2 (DP2) receptor antagonists

Starting with the weak agonist indomethacin, a series of potent, selective CRTh2 (DP(2)) antagonists have been discovered as potential treatments for asthma, allergic rhinitis and other inflammatory diseases.

Activity of the non-steroidal anti-inflammatory drug indomethacin against colorectal cancer

A substantial body of evidence from rodent colon carcinogenesis models, in vitro experiments with human colorectal cancer cells and limited clinical observations in humans suggest that the non-steroidal anti-inflammatory drug indomethacin has anti-colorectal cancer activity. However, although many mechanisms of the anti-neoplastic activity of indomethacin have been suggested, e.g., cyclooxygenase inhibition and peroxisome proliferator-activated receptor gamma activation, the precise relevance of the majority of in vitro pharmacological observations to the in vivo anti-neoplastic activity of indomethacin remains unclear. Herein, we review the existing literature describing the chemopreventative and chemotherapeutic efficacy of indomethacin against colorectal cancer, and draw together the disparate literature describing potential mechanisms of action of indomethacin in human colorectal cancer cells in vitro. Although indomethacin itself has significant adverse effects, including serious upper gastrointestinal toxicity, the development of novel derivatives that may have an improved safety profile means that further investigation of the anti-colorectal cancer activity of indomethacin is warranted.

Cutting edge: agonistic effect of indomethacin on a prostaglandin D2 receptor, CRTH2

Indomethacin is a widely used nonsteroidal anti-inflammatory drug and is generally known to exhibit its multiple biological functions by inhibiting cyclooxygenases or activating peroxisome proliferator-activated receptors. In this study, we present evidence demonstrating that the novel PGD(2) receptor chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) is another functional target for indomethacin. Indomethacin induced Ca(2+) mobilization in CRTH2-transfected K562 cells at submicromolar concentrations (approximate EC(50), 50 nM) in a G(alphai)-dependent manner as PGD(2) did. Other nonsteroidal anti-inflammatory drugs (aspirin, sulindac, diclofenac, and acemetacin) had no such effect even at micromolar concentrations. In chemotaxis assay, three CRTH2-expressing cell types, Th2 cells, eosinophils, and basophils, were all significantly attracted by indomethacin (EC(50), 50-500 nM) as well as by PGD(2) (EC(50), 2-20 nM), and the effects of indomethacin were blocked by anti-CRTH2 mAb. These results suggest the involvement of CRTH2 in mediating some of therapeutic and/or unwanted side effects of indomethacin, independently of cyclooxygenases and peroxisome proliferator-activated receptors.

Immunomodulatory effects of indomethacin and prostaglandin E2 on primary and secondary antibody response in growing layer hens

Effects of prostaglandin E2 (PGE2) and indomethacin, an inhibitor of PGE2 oxygenase, on primary and secondary antibody (Ab) responses to Mycobacterium butyricum protein or keyhole limpet hemocyanin (KLH) were studied in growing layer hens. Immunizations at 35 and 70 d of age were accompanied by immunomodulating treatments with PGE2, indomethacin, or PBS. In addition, we studied effects of various doses of indomethacin and PGE2 on mitogen-induced T-cell proliferation in vitro. Secondary Ab responses to KLH were enhanced by administration of indomethacin at secondary immunization and, to a lesser extent, by PGE2 administration at secondary immunization. Primary Ab responses to M. butyricum tended to decrease by administration of either PGE2 or indomethacin. Secondary Ab responses to M. butyricum were affected by administration of both PGE2 and indomethacin at primary immunization. Prostaglandin E2 increased phytohemagglutinin (PHA)-induced lymphocyte proliferation. Indomethacin decreased Concanavalin A (ConA)- and PHA-induced lymphocyte proliferation. The net effect of indomethacin on the Ab response could not be explained by inhibition of PGE2 oxygenase only. Our data rather suggest an inhibition by indomethacin of other immunosuppressing factors derived from arachidonic acid. We concluded that polyunsaturated fatty acid-derived products might especially affect secondary antibody responsiveness. This finding may depend on inhibition or enhancement of T-cell responsiveness. Consequently, immunomodulation by dietary polyunsaturated fatty acids may have profound effects at secondary rather than at primary exposure to pathogens.

Some studies on the rodenticidal action of indomethacin

The oral LD50 of indomethacin for a seven-day observation was found to be 12.58 +/- 1.15 mg/kg. At LD10 of 6.61 mg/kg, a dose to weight ratio of 28 was obtained for a 240 g rat, while at a maximum single dose of 3 mg/kg in man it is only 0.04. Neither diazepam nor phenobarbital influenced death at the doses of both drugs used. However, cholestyramine 2 g/kg/day was found to protect by 50% from the LD100 of indomethacin. Gross pathological studies showed dose-dependent ulceration and perforation (P < 0.001, 12 vs 24 mg/kg) and such lesions occurred in starved rats, were low in bile duct-ligated compared to sham-operated rats (P < 0.001) and were also low in cholestyramine-treated rats. Indomethacin-induced lethality in rats was found to be dose-dependent.

Desmoid tumour: a pleomorphic lesion

BACKGROUND

Desmoid tumour (DT) is an uncommon locally invasive non-metastasizing neoplastic lesion. The aetiology of this tumour is unknown and its treatment is controversial. Twelve cases of DT are presented and the literature is reviewed.

METHODS

Twelve cases of DT treated at our institution during a 3.5-year period are analysed and the literature reviewed. Ten patients were referred with a primary tumour, one with local recurrence and one patient with a second primary desmoid tumour. One patient had multiple mesenteric DT (familial adenomatous polyposis coli-FAP), and in the remaining 11 patients the tumour was located in the abdominal wall in four, at an extremity in three, in the upper back in two patients, in the pelvis in one and retroperitoneally in one.

RESULTS

The largest mesenteric DT was marginally excised en bloc with total jejunectomy. In the remaining 11 DT, complete excision to microscopically tumour-free margins was possible in nine cases and to microscopically involved margins in two cases. At a mean follow-up of 22 months (range 7-38 months), one patient was alive with stable disease (Gardner's syndrome), 10 patients were alive and free of recurrence and one patient (9%) developed local recurrence which was re-excised-she is disease-free 10 months later.

CONCLUSIONS

Complete excision is the main modality of treatment for primary and recurrent DT. This is feasible in most cases except for tumours involving the base of the bowel mesentery. Surgical resection alone achieved local control of the tumour in most of the patients in this series (92%).

Recovery of Ca2+ pools and growth in Ca2+ pool-depleted cells is mediated by specific epoxyeicosatrienoic acids derived from arachidonic acid

Depletion of Ca2+ pools using the irreversible Ca2+ pump blocker, thapsigargin, induces DDT1MF-2 smooth muscle cells to enter a stable nonproliferative state. Reversal of this state can be mediated by high (20%) serum treatment, which induces new Ca2+ pump protein, return of Ca2+ pools, and reentry of cells into the cell cycle; the effect of serum can be mimicked by the essential fatty acids (EFA), arachidonic, linoleic, and alpha-linolenic acids (Graber, M.N., Alfonso, A., and Gill, D.L., (1996) J. Biol. Chem. 271, 883-888). The possible requirement for EFA metabolism in inducing recovery of Ca2+ pool-depleted growth-arrested cells was investigated. Neither cyclooxygenase or lipoxygenase inhibitors had any effect on arachidonic acid-induced growth recovery of thapsigargin-treated cells. In contrast, the cytochrome P-450 epoxygenase inhibitors, SKF525A and metyrapone, substantially reduced arachidonic acid-induced recovery of growth while having minimal effects on control cell growth. Both epoxygenase inhibitors completely prevented the arachidonic acid-induced recovery of bradykinin-releasable Ca2+-pumping pools, whereas cyclooxygenase and lipoxygenase inhibitors had no effect. The effectiveness of the four cytochrome P-450 metabolites of arachidonic acid on recovery of Ca2+ pools were compared; 8,9- and 11,12-epoxyeicosatrienoic acid (EET) at 1.5 microM were completely effective in recovering agonist-sensitive Ca2+ pools, whereas the 5,6- and 14,15-EETs were without effect. SKF525A did not block the action of 8,9- or 11, 12-EET indicating further P-450 metabolism was not required. Hydration of the active EET molecules prevented Ca2+ pool recovery since the dihydroxy-derivatives of both 8,9- and 11,12-EET were ineffective. The specificity of effectiveness among EET molecules for subsequent resumption of growth of thapsigargin-treated cells was the same as for Ca2+ pool recovery. Significantly, the P-450 inhibitors, SKF525A and metyrapone, both prevented the action of 20% serum in inducing recovery of thapsigargin-treated cells, whereas cyclooxygenase and lipoxygenase inhibitors were ineffective, indicating that EFAs are the active component within serum that is responsible for recovery of Ca2+ pool-depleted cells. The specific action of EETs in mediating recovery of Ca2+ pools and growth of thapsigargin-treated cells represents not only a novel action of epoxygenase products from EFAs, but also a potentially significant new signaling pathway that may effect translational control and regulate transition from a stationary to proliferative growth state.

Oxidized low density lipoprotein stimulates protein kinase C (PKC) activity and expression of PKC-isotypes via prostaglandin-H-synthase in P388D1 cells

Treatment of P388D1 macrophage-like cells with oxLDL enhanced protein kinase C (PKC) activity in cell extracts. Similar effects were induced by acetylated LDL (acLDL) and maleylated albumin (malBSA). Treatment with oxLDL, acLDL and malBSA was also accompanied by increased production of prostaglandins as well as by an enhanced level of prostaglandin H synthase 2 (cyclooxygenase 2, COX 2). Modified (lipo)proteins differentially affected the levels of individual cytosolic PKC-isoenzymes. Effects of oxLDL on PKC activity/expression were abrogated by indometacin, by pre-exposure to the dual lipoxygenase/cyclooxygenase inhibitor ML 3000 and by treatment with N-(2-cyclohexyloxy-4-nitrophenyl)methane sulfonamide (NS-398). These results suggest a predominantly COX 2-dependent and isotype-specific effect of modified (lipo)proteins on PKC.

Pentadecapeptide BPC 157 positively affects both non-steroidal anti-inflammatory agent-induced gastrointestinal lesions and adjuvant arthritis in rats

Besides a superior protection of the pentadecapeptide BPC 157 (an essential fragment of an organoprotective gastric juice peptide BPC) against different gastrointestinal and liver lesions, an acute anti-inflammatory and analgetic activity was also noted. Consequently, its effect on chronic inflammation lesions, such as adjuvant arthritis, and non-steroidal anti-inflammatory agents (NSAIAs)-induced gastrointestinal lesions was simultaneously studied in rats. In gastrointestinal lesions (indomethacin (30 mg/kg s.c.), aspirin (400 mg/kg i.g.) and diclofenac (125 mg/kg i.p.) studies, BPC 157 (10 micrograms or 10 ng/kg i.p.) was regularly given simultaneously and/or 1 h prior to drug application (indomethacin). In the adjuvant arthritis (tail-application of 0.2 mL of Freund's adjuvant) studies (14 days, 30 days, 1 year) BPC 157 (10 micrograms or 10 ng/kg i.p.), it was given as a single application (at 1 h either before or following the application of Freund's adjuvant) or in a once daily regimen (0-14th day, 14-30th day, 14th day-1 year). Given with the investigated NSAIAs, BPC 157 consistently reduced the otherwise prominent lesions in the stomach of the control rats, as well as the lesions in the small intestine in the indomethacin groups. In the adjuvant arthritis studies, the lesion's development seems to be considerably reduced after single pentadecapeptide medication, and even more attenuated in rats daily treated with BPC 157. As a therapy of already established adjuvant arthritis, its salutary effect consistently appeared already after 2 weeks of medication and it could be clearly seen also after 1 year of application. Taking together all these results, the data likely point to a special anti-inflammatory and mucosal integrity protective effect.

Identification of casoxin C, an ileum-contracting peptide derived from bovine kappa-casein, as an agonist for C3a receptors

Casoxin C (Tyr-Ile-Pro-Ile-Gln-Tyr-Val-Leu-Ser-Arg) is a bioactive peptide that was isolated from a tryptic digest of bovine kappa-casein as an anti-opioid peptide in longitudinal strips of guinea pig ileum. Casoxin C also evokes contraction of the ileal strips, and we found that this process was biphasic with rapid and slow components. The contractile profile was very similar to that of human complement C3a(70-77), which is the COOH-terminal octapeptide of C3a and has, although less potent, qualitatively the same biological activities as C3a. Casoxin C also has homology with C3a(70-77). The rapid contraction was mediated by histamine release and the slow contraction was mediated by a prostaglandin E2-like substance, judging from the effects of various pharmacological inhibitors and antagonists on the ileal contraction. Casoxin C had affinity for C3a receptors (IC50 = 40 microM) in the radioreceptor assay. In addition, casoxin C showed phagocyte-stimulating activities. Casoxin C is therefore the first milk-derived peptide identified, that acts through complement C3a receptors.

NSAID-induced polyp regression in familial adenomatous polyposis patients

NSAIDs inhibit prostaglandin synthesis. In 1983, Waddell et al first reported that sulindac, a NSAID (Clinoril), caused regression of rectal adenomatous polyps in several patients with familial adenomatous polyposis, an inherited form of colorectal cancer. Subsequently, NSAIDs have been used as chemopreventive agents in animal carcinogenesis models and adenoma regression had been confirmed in human trials with sulindac. This article summarizes these developments and describes possible mechanisms of colorectal neoplasia chemoprevention.

Sulindac induced regression of colorectal adenomas in familial adenomatous polyposis: evaluation of predictive factors

BACKGROUND

Sulindac, a non-steroidal anti-inflammatory drug, causes regression of colorectal adenomas in patients with familial adenomatous polyposis (FAP) but the response is variable. Specific clinical factors predictive of sulindac induced regression have not been studied.

METHODS

22 patients with FAP were given sulindac 150 mg orally twice a day. Polyp number and size were determined before treatment and at three months. The relation of nine clinical factors to polyp regression (per cent of baseline polyp number after treatment) was evaluated by univariate and multivariate analysis.

RESULTS

After three months of sulindac, polyp number had decreased to 45 per cent of baseline and polyp size to 50 per cent of baseline (p < 0.001 and p < 0.01, respectively). Univariate analysis showed greater polyp regression in older patients (p = 0.004), those with previous colectomy and ileorectal anastomosis (p = 0.001), and patients without identifiable mutation of the APC gene responsible for FAP (p = 0.05). With multivariate regression analysis, response to sulindac treatment was associated with previous subtotal colectomy.

CONCLUSIONS

Sulindac treatment seems effective in producing regression of colorectal adenomas of FAP patients with previous subtotal colectomy regardless of baseline polyp number and size. Changed sulindac metabolism, reduced area of the target mucosa, or changed epithelial characteristics after ileorectal anastomosis may explain these findings.

hP, the component of log P controlling structure-activity relationships amongst non-steroidal anti-inflammatory drugs

A range of 25 drugs and other compounds selected from published sources by strict criteria, has been used to confirm that their ability to inhibit the production of prostaglandin by mouse peritoneal macrophage does not correlate with log P but with hP, the parameter composed of only the hydrophobic contributions (atoms and groups composed of carbon, hydrogen and halogens). Other heteroatoms and physical properties can usually be ignored. Anti-inflammatory activity does not depend upon pKa or partition phenomena unless extreme, nor does it depend primarily upon the structural types within the range phenols, salicylic acids, mefenamic acids, areneacetic and profenic acids.

Studies on the ileum-contracting mechanisms and identification as a complement C3a receptor agonist of oryzatensin, a bioactive peptide derived from rice albumin

Oryzatensin (Gly-Tyr-Pro-Met-Tyr-Pro-Leu-Pro-Arg) is an ileum-contracting and immunostimulating peptide derived from rice albumin. The mechanisms for the ileal contraction that it induces, consisting of rapid and slow components, were examined. The rapid contraction was mediated by histamine release and the slow contraction by a prostaglandin E2-like substance, judging from the effects of various pharmacological inhibitors and antagonists on ileal contraction and titration of histamine release. The contractile profile was very similar to that of human complement C3a(70-77), which is the COOH-terminal octapeptide of C3a and has, although less potent, qualitatively the same biological activities as C3a. Oryzatensin showed homology with C3a(70-77) and affinity for C3a receptors (IC50 = 44 microM) by radioreceptor assay. This is the first report of a food-derived bioactive peptide acting through complement C3a receptors.

Sensitive fused-silica capillary gas chromatographic assay using electron-capture detection for indomethacin in ovine fetal fluids

A sensitive gas chromatographic (GC) method with electron-capture detection (ECD) has been developed to quantitate indomethacin (IND) in plasma, urine, amniotic, and tracheal fluids obtained from the pregnant sheep model. IND and the internal standard, alpha-methylindomethacin (alpha-Me-IND) are extracted by a simple liquid-liquid extraction procedure using ethyl acetate and derivatized with N-methyl-N-(tert.-butyldimethyl-silyl)trifluoroacetamide (MTBSTFA) at 60 degrees C for 50 min. The limit of quantitation (LOQ) is 1 ng/ml with a C.V. < 10% and signal-to-noise ratio > 10. Recoveries from all fluids were greater than 80%. Calibration curves were linear over the range of 1-32 ng/ml with a coefficient of determination (r2) > 0.999. Inter- and intra-day coefficients of variation were < 10% at concentrations of 2-32 ng/ml, and < 20% at the LOQ. Applicability of the developed method is demonstrated for a pharmacokinetic study of IND samples collected following long-term infusion of IND in a chronically instrumented ovine fetus.

Complete reversion and prevention of rectal adenomas in colectomized patients with familial adenomatous polyposis by rectal low-dose sulindac maintenance treatment. Advantages of a low-dose nonsteroidal anti-inflammatory drug regimen in reversing adenomas exceeding 33 months

PURPOSE

This nonrandomized, controlled Phase II pilot study aims at the lowest effective dose of rectally applied sulindac to achieve and maintain adenoma reversion in colectomized patients with familial adenomatous polyposis (FAP).

METHODS

The study group (n = 15) underwent proctoscopic and laboratory follow-up for polyp reversion every 6 to 12 weeks. Polyp reversion was followed by dose reduction in predefined steps. Proliferating cell nuclear antigen/cyclin (PCNA) and KI-67 proliferation indices (PI) were performed by point counting. Prostaglandin (PG)E2 and PGF2 alpha were quantified by time-resolved competitive fluorescence immunoassay.

RESULTS

All patients responded to therapy within 6 to 24 weeks. Sixty and 87 percent of patients achieved complete adenoma reversion after 48 weeks at 53 and 67 mg of sulindac per day per patient on average, respectively. Reversion was evident compared with the control group. Dose reduction by one-sixth to one-eighth of the usual oral dose was significant (Mann's trend test, P < 0.05). PCNA and KI-67 PIs of adenomatous and flat mucosa were significantly reduced (Wilcoxon's test, P < 0.05). Correlation of PCNA and KI-67 PIs indicate similar reaction of different tissue structures (Spearman's rank correlation test, P < 0.01). Nonsteroidal anti-inflammatory drug-induced redifferentiation from high-grade to low-grade dysplasia occurred in all but two patients. Tissue-PGE2 levels were greatly reduced. Unwanted, curable side effects were rare (gastritis, n = 2), and laboratory controls are within detection limits.

CONCLUSIONS

Low-dose rectal sulindac maintenance therapy is highly effective in achieving complete adenoma reversion without relapse in 87 percent of patients after 33 months. Rectal FAP phenotype should be crucial for the surgical decision. Colectomy with ileorectal anastomosis and regular chemoprevention might proceed to be a promising alternative to pouch procedures. Chemoprevention with lower incidence of FAP-related tumors via dysplasia reversion may be possible in the future.

Adenomatous polyposis coli, protein kinases, protein tyrosine phosphatase: the effect of sulindac

A putative explanation of the effect of sulindac on adenomatous colon and duodenal polyps from clinical observations and related in vitro experiments is presented. In cells with mutant APC genes, persistent high prostaglandin content of polyps leads to desensitization, downregulation of adenylate cyclase, uncoupling of cAMP synthesis from prostaglandin, and inactivation of protein kinase A (PKA). It is suggested that in normal cells, (APC) protein binds to catenins and microtubules to maintain structure and contribute to cell-cell communication, adherence, and the dephosphorylated state, a necessary condition for such functions. Cells with mutant APC product become isolated, deprived of communication and adhesion to other epithelial cells, overphosphorylated, and without corrective capability. The latter is largely due to downregulation of cAMP synthesis and protein kinase A activity secondary to high prostaglandin. Three main biochemical defects ensue: (1) the restrictive influence of PKA catalyzed phosphorylation of Raf-1 kinase and resultant effects on the MAP kinase cascade and transcription is lost, (2) the transcription of immediate early genes, including cyclooxygenase is stimulated, and (3) the stimulation of protein tyrosine phosphatase (PTPase) by PKA is in abeyance. These putative abnormalities are reversed by inhibition of cyclooxygenase-1 by sulindac. cAMP synthesis and PKA activity return to normal. PKA catalyzed phosphorylations block Raf-1 kinase at the confluence of the Ras and protein kinase C pathways. The MAP kinase cascade is inhibited as is transcription of immediate early genes. At the same time PKA stimulates PTPase, which dephosphorylates the cytoskeleton and restores cell-cell communication, adherence, and structure. The transformed phenotype is circumvented by adjustment of the phosphorylation state and mutant cells rejoin the epithelial community. The redox state of cytoplasm in mutant cells may be shifted toward reduction.

Autonomic modulation of action potential and tension in guinea pig papillary muscles

The effects of alpha 1-adrenoceptor and muscarinic acetylcholine receptor stimulation on action potential and tension were studied in guinea pig papillary muscles obtained from both right and left ventricles. Stimulation of muscarinic acetylcholine receptors with carbachol produced a reduction of the action potential duration and a positive inotropic effect in papillary muscles from both ventricles. Both effects were concentration dependent and atropine sensitive. However, differential responsiveness was found upon alpha 1-adrenoceptor activation in muscles obtained from left and right ventricles. In right side papillary muscles, the alpha 1-adrenoceptor agonist, methoxamine, decreased the action potential duration and produced a positive inotropic effect. In contrast, methoxamine decreased the action potential duration but failed to produce a positive inotropic effect in left side papillary muscles. All methoxamine effects were antagonized by prazosin. Responses to maximum concentration of carbachol and methoxamine on the action potential duration and contractility were additive in right side papillary muscles. Phorbol 12,13-dibutyrate (PDB), a direct protein kinase C activator, also decreased the action potential duration in a manner that was additive to both carbachol and methoxamine. However, PDB reversed the positive inotropic effect of carbachol and methoxamine. The methoxamine-induced shortening of the action potential duration was prevented by pretreatment with indomethacin and nordihydroguaiaretic acid, blockers of arachidonic acid metabolism, but not by the protein kinase C antagonist, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7).(ABSTRACT TRUNCATED AT 250 WORDS)

Sulindac and polyp regression

Sulindac is useful in regression of adenomatous polyps. In addition to orally administered sulindac, rectal preparations also appear to be efficacious [32]. However, further studies are necessary to determine whether regression of adenomas, the precursor of colorectal cancer, will cause decrease in colorectal cancer risk in both FAP and non FAP patients. Moreover, clinical studies are needed to test the application of this potential chemopreventative drug in several other patient populations. Several interesting observations have been made concerning the use of sulindac. Indomethacin, a related NSAID to sulindac, did not cause polyp regression. Also, upper gastrointestinal tract polyps in the stomach and duodenum appear not to be affected by sulindac therapy. These observations might be explained by the metabolism of sulindac in which the pharmacologically active sulfide metabolite is generated and distributed in the large intestine. Also, investigators noted that after discontinuation of sulindac adenomas recurred. Sulindac treatment was well tolerated at the usual clinical doses. Although some investigators have speculated on the effect of prostaglandin inhibition sulindac on cAMP-dependent mechanisms which control cellular proliferation [33], the cause of adenoma regression is unknown. There is evidence that colorectal endogenous prostaglandin levels decrease with sulindac. Evaluation of colorectal mucosal cellular proliferation in patients treated with sulindac has revealed a decrease in labelling index by bromodeoxyuridine labeling in one study [28] but no change in labelling index by [3H]thymidine incorporation in another investigation [34]. Also, ki 67 labelling index, another measure of cellular proliferation, was not affected in the colorectal mucosa of patients taking sulindac.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of arachidonic acid metabolism in somatostatin and substance P effects on inward rectifier K conductance in rat brain neurons

Somatostatin enhances an inward rectifier K conductance in cultured locus coeruleus neurons, while substance P reduces an inward rectifier K conductance in cultured nucleus basalis and locus coeruleus neurons. The role of arachidonic acid metabolites in these responses was studied. The somatostatin-induced response was reduced by phospholipase A2 inhibitors, non-specific lipoxygenase inhibitors and specific 5-lipoxygenase inhibitors. A cyclooxygenase inhibitor and a 12-lipoxygenase inhibitor had no effect. 5(S)-HPETE occasionally increased the K conductance, but failed to occlude the somatostatin response. The substance P response was suppressed by a 5-lipoxygenase inhibitor but not by a 12-lipoxygenase inhibitor. These results suggest that the 5-lipoxygenase pathway is not a specific messenger of either one of these responses, but that it plays a more general role in maintaining or enhancing the effectiveness of both somatostatin and substance P responses.

Prostaglandins and inhibitors of arachidonate metabolism suppress experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an autoimmune inflammatory disease of the central nervous system (CNS). It is an animal model of post-infectious encephalomyelitis and multiple sclerosis (MS). Acute EAE is mediated by macrophages and by T helper 1 (Th1) lymphocytes directed against brain antigens. Inflammation in EAE could potentially be modified by prostaglandins (PG) secreted by blood monocytes (Mo) and brain glial cells. PGE elevates cAMP, which inhibits Mo function and selectively blocks secretion of cytokines by Th1 cells. In the present study, we found that a long-acting PGE1 analogue (LAPGE) inhibited clinical and histological EAE. Indomethacin (INDO) also suppressed active EAE. The combination of INDO plus LAPGE inhibited disease further, possibly by allowing LAPGE to function unopposed by immunostimulatory PG. EAE was suppressed when these agents were administered from the time of immunization or from the onset of clinical disease. The combination of INDO plus LAPGE also inhibited delayed-type hypersensitivity (DTH) reactions to myelin basic protein (MBP), and diminished in vitro lymphocyte responses to mitogens and MBP. PGE analogues and modifiers of arachidonate metabolism block autoimmune responses to brain antigens in vitro and in vivo, and may ameliorate inflammatory and autoimmune diseases of the brain and other organs.

Inhibition of respiratory burst in macrophages by complement receptor blockade

Respiratory burst activity was induced in rat peritoneal macrophages by opsonized zymosan. Inhibitors were tested by administering them before or after the inducing agent: OX-42, an anti-rat macrophage complement receptor type 3 antibody, was active at an estimated concentration of 2.1 nM, and was more than 100-fold more potent when administered before, rather than after, opsonized zymosan. Indomethacin and dapsone, two agents with antiinflammatory activity, were also more effective before opsonized zymosan, but only in the 10(-3) to 10(-4) molar range. Inhibitors of eicosanoid synthesis, as well as the antiinflammatory prostaglandin E2, also reduced the respiratory burst.

Changes in prostaglandin E2 and F2 alpha during vitellogenesis in the Florida crayfish Procambarus paeninsulanus

While the role of eicosanoids in reproduction in vertebrate species has been well established, the role of these fatty acid derivatives in invertebrate species has not been as well characterized. The purpose of this study was to investigate changes in prostaglandins E2 and F2 alpha during vitellogenesis in the crayfish Procambarus paeninsulanus. In homogenates of crayfish ovaries taken at various stages of development, the rate of prostaglandin synthesis and the concentrations of prostaglandins E2 and F2 alpha increased during the final stages of yolk production just prior to ovulation. A gradual increase in prostaglandin E2 amounts was observed throughout the progression of vitellogenesis. The data suggests the possible involvement of prostaglandins in regulatory events associated with vitellogenesis and the induction of ovulation in Procambarus paeninsulanus.

Motor effects of indomethacin, morphine or vagal nerve stimulation on the feline small intestine in vivo

Some factors known to affect jejunal motility (recorded as volume changes of an intraluminal balloon) were investigated in anaesthetized cats (ether-chloralose) pretreated with guanethidine and atropine. Indomethacin, morphine (both compounds administered systemically) or vagal nerve stimulation elicited jejunal excitatory motor responses. The effect of indomethacin seemed to be independent of cyclooxygenase inhibition and probably did not involve opioid receptors. It is suggested that the spasmogenic stimuli caused jejunal hypermotility by inhibiting tonically active, inhibitory motor neurons that are intrinsic to the gut. Furthermore, when the jenunal tone had been raised by indomethacin or morphine spontaneous relaxations were observed, and these could be mimicked by vagal stimulation. Hexamethonium antagonized these relaxations but did not attenuate the drug-induced jejunal hypermotility.

Central and peripheral prostaglandins are involved in sickness behavior in birds

Many of the behavioral manifestations of mammals and birds following infection are now recognized as important mechanisms for maintaining homeostasis and promoting recovery. To investigate the role of prostaglandins (PGs) in the behavioral and physiological effects of lipopolysaccharide (LPS) in birds, chickens were injected with indomethacin (Ind) peripherally (IP, 5 mg) or centrally (ICV, 100 micrograms) and their behavior and body temperature following a challenge IP injection of LPS (2.5 mg) were assessed at 1 and 2 h, respectively. Pretreatment with Ind IP or ICV completely inhibited the hyperthermia caused by LPS. Ind injected IP but not ICV significantly attenuated the LPS-induced anorexia. The drowsiness caused by LPS was completely inhibited by Ind injected IP and partially inhibited by Ind administered ICV. These results are interpreted to indicate that LPS induces hyperthermia in the chicken by activating a PG system in the brain. Peripheral PGs appear to be involved in the anorectic response to LPS, whereas drowsiness caused by LPS may involve both peripheral and central PGs. These data are consistent with the hypothesis that multiple PG systems are activated during the acute-phase response, which may explain the dissociation between mechanisms controlling the behavioral and physiological responses to infection.

Testolactone, sulindac, warfarin, and vitamin K1 for unresectable desmoid tumors

Ten patients with large inoperable desmoid tumors in various body locations were treated with testolactone. Four tumors (40%) responded with major regressions, i.e., more than 50% reduction in volume. Eight patients received nonsteroid anti-inflammatory drugs (indomethacin, sulindac, or sulindac with warfarin and vitamin K1 [Mephyton]) for periods of 2 to 91 months. There was one major regression, one partial regression, and three instances of tumor growth arrest over periods up to 8 years. Seven patients were treated with nonsteroid anti-inflammatory drugs concurrent with or after testolactone or tamoxifen. There were five major regressions and one partial regression with extensive central necrosis of an enormous intra-abdominal tumor. The last patient has been treated for only 12 months, with no change in tumor volume. It appears that estrogens function as growth factors for desmoid tumors, and that minimization of these effects inhibits tumor growth in some, but not all, cases. In those instances where antiestrogens were not effective as single agents, the tumors usually responded to subsequent nonsteroid anti-inflammatory drug therapy. Withdrawal of estrogen may be followed by inhibition of transcription of genes that support tumor cell proliferation, and sulindac and indomethacin may augment these effects by inhibiting prostaglandin and cyclic AMP synthesis and the activity of protein kinase C. Warfarin may function as a protonophore to acidify the cytoplasm and prevent the alkalinization that is necessary to initiate DNA synthesis and cell cycle progression, again an impairment of the transcription process.

Arachidonic acid modulates hippocampal calcium current via protein kinase C and oxygen radicals

Arachidonic acid (AA) is a second messenger liberated via receptor activation of phospholipase A2 or diacylglycerol-lipase. We used whole-cell voltage clamp of acutely isolated hippocampal CA1 pyramidal cells to investigate the hypothesis that AA modulates Ca2+ channel current (ICa) via activation of protein kinase C (PKC) and generation of free radicals. AA depressed ICa in a dose- and time-dependent manner similar to that previously reported for the action of phorbol esters on ICa. A similar depression was seen with a xanthine-based free radical generating system. The specific PKC inhibitor PKCI (19-36), the protein kinase inhibitor H-7, and the superoxide free radical scavenger SOD each blocked ICa depression by 70%-80%. Complete block of the AA response occurred when SOD was used simultaneously with a PKC inhibitor. These data suggest that PKC and free radicals play a role in AA-induced suppression of ICa.

Possible involvement of arachidonic acid metabolites of cytochrome P450 monooxygenase pathway in vasopressin-stimulated glycogenolysis in isolated rat hepatocytes

Arachidonic acid (AA) is reported to be metabolized by three major pathways, i.e., cyclooxygenase (CO), lipoxygenase (LO), and NADPH-dependent cytochrome P450 monooxygenase (MO) pathways. Monooxygenase metabolites of AA have been proposed to play an important role in hormone action in various cells. Recently it was reported that the MO pathway may exist in rat liver. The present study was carried out to investigate the role of MO metabolites in vasopressin-induced glycogenolysis in isolated rat hepatocytes. The pretreatment of isolated rat hepatocytes with eicosatetraynoic acid (ETYA), an inhibitor of CO, LO, and MO pathways, and ketoconazole and SKF 525A, inhibitors of the MO pathway, dose-dependently reduced vasopressin-induced phosphorylase activation, while the pretreatment with indomethacin, an inhibitor of the CO pathway, had no effect. The increment of cytosolic calcium concentration in vasopressin-stimulated hepatocytes was also dose-dependently decreased by ETYA, ketoconazole, and SKF 525A. In vitro addition of epoxyeicosatrienoic acid (EET) dose-dependently increased both phosphorylase a activity and cytosolic calcium concentration. 14,15-EET was the most potent among four regioisomeric EETs. These results suggest that MO metabolites of AA, most likely EETs, may be involved in vasopressin-induced glycogenolysis probably via the activation of phosphorylase by increasing the cytosolic calcium concentration.

Action of noradrenaline on isolated proximal and distal coronary arteries of rat: selective release of endothelium-derived relaxing factor in proximal arteries

1. The effect of noradrenaline (NA) on the vascular smooth muscle and endothelial cells in isolated ring segments from the proximal and distal part of the left coronary artery (LCA) in rats was examined. 2. NA had a weak concentration-dependent contractile effect on proximal but relaxed distal segments of the LCA. The maximal NA-induced contraction of the proximal segments was doubled while the relaxation of the distal LCA segments was converted to a contraction after blockade of beta-adrenoceptors with propranolol 3 x 10(-6) M, thus indicating the presence of both alpha- and beta-adrenoceptors in the arteries, with dominance of alpha-adrenoceptors and of beta-adrenoceptors in the proximal and distal segments of the LCA, respectively. 3. The contractile effect of NA (beta-adrenoceptors blocked) was doubled in the proximal LCA segments after the endothelium was removed. Endothelial denudation had, in contrast, no potentiating effect on the contractile response of the distal arteries to NA. Both proximal and distal segments became more sensitive to the contractile action of NA after removal of the endothelium. 4. The spontaneous myogenic tone increased in both proximal and distal LCAs after endothelial removal, indicating spontaneous release of a relaxing endothelial factor in the vessels. 5. Following contraction with prostaglandin F2 alpha (PGF2 alpha), and in the presence of propranolol, 3 x 10(-6) M, and prazosin, 10(-6) M, NA induced an endothelium-dependent relaxation of only proximal but not distal segments of the precontracted LCA. The NA-induced relaxation of the proximal segments of the LCA was not altered by indomethacin 10- M but was completely abolished after incubation with methylene blue, 3 x 10-6 M, or following endothelium removal. These results are compatible with NA-induced release of EDRF in these arteries. 6. The selective alpha 2-adrenoceptor agonist, B-HT 933, only induced a weak relaxation of PGF2 alpha,-precontracted proximal (endothelium intact) LCA segments at a concentration of 10-4M. The NA-induced relaxation of these vessels was unaffected by incubating the vessels with 10- IM B-HT 933. The NA relaxation response curve was shifted ca 1.1 log unit to the right by rauwolscine, 1o- 6M, giving an estimated pA2-value of 7.12. The receptor through which NA activates the endothelium appears to be of an atypical alpha 2-subtype.