Selective potentiation of drug cytotoxicity by NSAID in human glioma cells: the role of COX-1 and MRP

Targeting fatty acid metabolism in glioblastoma

Glioblastoma (GBM) is a primary tumor of the brain defined by its uniform lethality and resistance to conventional therapies. There have been considerable efforts to untangle the metabolic underpinnings of this disease to find novel therapeutic avenues for treatment. An emerging focus in this field is fatty acid (FA) metabolism, which is critical for numerous diverse biological processes involved in GBM pathogenesis. These processes can be classified into four broad fates: anabolism, catabolism, regulation of ferroptosis, and the generation of signaling molecules. Each fate provides a unique perspective by which we can inspect GBM biology and gives us a road map to understanding this complicated field. This Review discusses the basic, translational, and clinical insights into each of these fates to provide a contemporary understanding of FA biology in GBM. It is clear, based on the literature, that there are far more questions than answers in the field of FA metabolism in GBM, and substantial efforts should be made to untangle these complex processes in this intractable disease.

Targeting multidrug resistance-associated protein 1 (MRP1)-expressing cancers: Beyond pharmacological inhibition

Resistance to chemotherapy remains one of the most significant obstacles to successful cancer treatment. While inhibiting drug efflux mediated by ATP-binding cassette (ABC) transporters is a seemingly attractive and logical approach to combat multidrug resistance (MDR), small molecule inhibition of ABC transporters has so far failed to confer clinical benefit, despite considerable efforts by medicinal chemists, biologists, and clinicians. The long-sought treatment to eradicate cancers displaying ABC transporter overexpression may therefore lie within alternative targeting strategies. When aberrantly expressed, the ABC transporter multidrug resistance-associated protein 1 (MRP1, ABCC1) confers MDR, but can also shift cellular redox balance, leaving the cell vulnerable to select agents. Here, we explore the physiological roles of MRP1, the rational for targeting this transporter in cancer, the development of small molecule MRP1 inhibitors, and the most recent developments in alternative therapeutic approaches for targeting cancers with MRP1 overexpression. We discuss approaches that extend beyond simple MRP1 inhibition by exploiting the collateral sensitivity to glutathione depletion and ferroptosis, the rationale for targeting the shared transcriptional regulators of both MRP1 and glutathione biosynthesis, advances in gene silencing, and new molecules that modulate transporter activity to the detriment of the cancer cell. These strategies illustrate promising new approaches to address multidrug resistant disease that extend beyond the simple reversal of MDR and offer exciting routes for further research.

Synthesis and biological evaluation of novel quinoline analogs of ketoprofen as multidrug resistance protein 2 (MRP2) inhibitors

Objectives

A new series of quinoline analogs of ketoprofen was designed and synthesized as multidrug resistance protein 2 (MRP2) inhibitors using ketoprofen as the lead compounds.

Materials and Methods

The cytotoxic activity of the compounds was evaluated againt two cancer cell lines including A2780/RCIS (MRP2-overexpressing ovarian carcinoma), A2780, drug-sensitive ovarian carcinoma using MTT assay. Compounds showing low toxicity in MTT test were selected to investigate their MRP inhibition activity. MRP2 inhibitory potency was evaluated by determination of the uptake amount of fluorescent 5-carboxy fluorescein diacetate (5-CFDA) substrate, by A2780/RCIS in the presence of the selected compounds. Mode of interaction between synthesized ligands and homology modeled MRP2 was investigated by MOE software.

Results

Compound 6d, a 4-carboxy quinoline possessing dimethoxy phenyl in position 2 of quinoline ring, showed the most MRP2 inhibition activity among all the quinolines and more than the reference drug ketoprofen. MRP2 inhibition activity of compound 7d was less in comparison to that of compound 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2. Docking studies showed that compound 7d methyl ester of 6d, interacted less compared to its parent 6d, which is consistent with biological results.

Conclusion

This study indicates that 6- or 8-benzoyl-2-arylquinoline is a suitable scaffold to design MRP2 inhibitors. The position of benzoyl in quinoline ring is important in inhibition of MRP2. Generally, MRP2 inhibition activity of compound 7d was less in comparison to that of 6d, indicating that carboxyl group in position 4 of quinoline may interact with MRP2.

Modulation of γ-Secretase Activity by a Carborane-Based Flurbiprofen Analogue

All over the world, societies are facing rapidly aging populations combined with a growing number of patients suffering from Alzheimer's disease (AD). One focus in pharmaceutical research to address this issue is on the reduction of the longer amyloid-β (Aβ) fragments in the brain by modulation of γ-secretase, a membrane-bound protease. R-Flurbiprofen (tarenflurbil) was studied in this regard but failed to show significant improvement in AD patients in a phase 3 clinical trial. This was mainly attributed to its low ability to cross the blood-brain barrier (BBB). Here, we present the synthesis and in vitro evaluation of a racemic meta-carborane analogue of flurbiprofen. By introducing the carborane moiety, the hydrophobicity could be shifted into a more favourable range for the penetration of the blood-brain barrier, evident by a logD7.4 value of 2.0. Furthermore, our analogue retained γ-secretase modulator activity in comparison to racemic flurbiprofen in a cell-based assay. These findings demonstrate the potential of carboranes as phenyl mimetics also in AD research.

The Process and Regulatory Components of Inflammation in Brain Oncogenesis

Central nervous system tumors comprising the primary cancers and brain metastases remain the most lethal neoplasms and challenging to treat. Substantial evidence points to a paramount role for inflammation in the pathology leading to gliomagenesis, malignant progression and tumor aggressiveness in the central nervous system (CNS) microenvironment. This review summarizes the salient contributions of oxidative stress, interleukins, tumor necrosis factor-α(TNF-α), cyclooxygenases, and transcription factors such as signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) and the associated cross-talks to the inflammatory signaling in CNS cancers. The roles of reactive astrocytes, tumor associated microglia and macrophages, metabolic alterations, microsatellite instability, O⁶-methylguanine DNA methyltransferase (MGMT) DNA repair and epigenetic alterations mediated by the isocitrate dehydrogenase 1 (IDH1) mutations have been discussed. The inflammatory pathways with relevance to the brain cancer treatments have been highlighted.

In vitro antiglioma action of indomethacin is mediated via AMP-activated protein kinase/mTOR complex 1 signalling pathway

We investigated the role of the intracellular energy-sensing AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in the in vitro antiglioma effect of the cyclooxygenase (COX) inhibitor indomethacin. Indomethacin was more potent than COX inhibitors diclofenac, naproxen, and ketoprofen in reducing the viability of U251 human glioma cells. Antiglioma effect of the drug was associated with p21 increase and G₂M cell cycle arrest, as well as with oxidative stress, mitochondrial depolarization, caspase activation, and the induction of apoptosis. Indomethacin increased the phosphorylation of AMPK and its targets Raptor and acetyl-CoA carboxylase (ACC), and reduced the phosphorylation of mTOR and mTOR complex 1 (mTORC1) substrates p70S6 kinase and PRAS40 (Ser183). AMPK knockdown by RNA interference, as well as the treatment with the mTORC1 activator leucine, prevented indomethacin-mediated mTORC1 inhibition and cytotoxic action, while AMPK activators metformin and AICAR mimicked the effects of the drug. AMPK activation by indomethacin correlated with intracellular ATP depletion and increase in AMP/ATP ratio, and was apparently independent of COX inhibition or the increase in intracellular calcium. Finally, the toxicity of indomethacin towards primary human glioma cells was associated with the activation of AMPK/Raptor/ACC and subsequent suppression of mTORC1/S6K. By demonstrating the involvement of AMPK/mTORC1 pathway in the antiglioma action of indomethacin, our results support its further exploration in glioma therapy.

The novel agent phospho-glycerol-ibuprofen-amide (MDC-330) inhibits glioblastoma growth in mice: an effect mediated by cyclin D1

Given that glioblastoma multiforme (GBM) is associated with poor prognosis, new agents are urgently needed. We developed phospho-glycerol-ibuprofen-amide (PGIA), a novel ibuprofen derivative, and evaluated its safety and efficacy in preclinical models of GBM, and its mechanism of action using human GBM cells and animal tumor models. Furthermore, we explored whether formulating PGIA in polymeric nanoparticles could enhance its levels in the brain. PGIA was 3.7- to 5.1-fold more potent than ibuprofen in suppressing the growth of human GBM cell lines. PGIA 0.75× IC50 inhibited cell proliferation by 91 and 87% in human LN-229 and U87-MG GBM cells, respectively, and induced strong G1/S arrest.In vivo, compared with control, PGIA reduced U118-MG and U87-MG xenograft growth by 77 and 56%, respectively (P< 0.05), and was >2-fold more efficacious than ibuprofen. Normal human astrocytes were resistant to PGIA, indicating selectivity. Mechanistically, PGIA reduced cyclin D1 levels in a time- and concentration-dependent manner in GBM cells and in xenografts. PGIA induced cyclin D1 degradation via the proteasome pathway and induced dephosphorylation of GSK3β, which was required for cyclin D1 turnover. Furthermore, cyclin D1 overexpression rescued GBM cells from the cell growth inhibition by PGIA. Moreover, the formulation of PGIA in poly-(L)-lactic acid poly(ethylene glycol) polymeric nanoparticles improved its pharmacokinetics in mice, delivering PGIA to the brain. PGIA displays strong efficacy against GBM, crosses the blood-brain barrier when properly formulated, reaching the target tissue, and establishes cyclin D1 as an important molecular target. Thus, PGIA merits further evaluation as a potential therapeutic option for GBM.

Ibuprofen and Diclofenac Restrict Migration and Proliferation of Human Glioma Cells by Distinct Molecular Mechanisms

Background

Non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with anti-tumorigenic effects in different tumor entities. For glioma, research has generally focused on diclofenac; however data on other NSAIDs, such as ibuprofen, is limited. Therefore, we performed a comprehensive investigation of the cellular, molecular, and metabolic effects of ibuprofen and diclofenac on human glioblastoma cells.

Methods

Glioma cell lines were treated with ibuprofen or diclofenac to investigate functional effects on proliferation and cell motility. Cell cycle, extracellular lactate levels, lactate dehydrogenase-A (LDH-A) expression and activity, as well as inhibition of the Signal Transducer and Activator of Transcription 3 (STAT-3) signaling pathway, were determined. Specific effects of diclofenac and ibuprofen on STAT-3 were investigated by comparing their effects with those of the specific STAT-3 inhibitor STATTIC.

Results

Ibuprofen treatment led to a stronger inhibition of cell growth and migration than treatment with diclofenac. Proliferation was affected by cell cycle arrest at different checkpoints by both agents. In addition, diclofenac, but not ibuprofen, decreased lactate levels in all concentrations used. Both decreased STAT-3 phosphorylation; however, diclofenac led to decreased c-myc expression and subsequent reduction in LDH-A activity, whereas treatment with ibuprofen in higher doses induced c-myc expression and less LDH-A alteration.

Conclusions

This study indicates that both ibuprofen and diclofenac strongly inhibit glioma cells, but the subsequent metabolic responses of both agents are distinct. We postulate that ibuprofen may inhibit tumor cells also by COX- and lactate-independent mechanisms after long-term treatment in physiological dosages, whereas diclofenac mainly acts by inhibition of STAT-3 signaling and downstream modulation of glycolysis.

Optimization of a cisplatin model of chemotherapy-induced peripheral neuropathy in mice: use of vitamin C and sodium bicarbonate pretreatments to reduce nephrotoxicity and improve animal health status

Background

Cisplatin, a platinum-derived chemotherapeutic agent, produces antineoplastic effects coupled with toxic neuropathic pain and impaired general health status. These side-effects complicate long term studies of neuropathy or analgesic interventions in animals. We recently demonstrated that pretreatment with sodium bicarbonate (4% NaHCO₃) prior to cisplatin (3 mg/kg i.p. weekly up to 5 weeks) was associated with improved health status (i.e. normal weight gain, body temperature, creatinine and ketone levels, and kidney weight ratio) in rats (Neurosci Lett 544:41-46, 2013). To reduce the nephrotoxic effects of cisplatin treatment in mice, we compared effects of sodium bicarbonate (4% NaHCO₃ s.c_.), vitamin C (25 mg/kg s.c_.), resveratrol (25 mg/kg s.c_.) and saline (0.9% NaCl) pretreatment on cisplatin-induced changes in animal health status, neuropathic pain and proinflammatory cytokine levels in spinal cord and kidney.

Results

Cisplatin-treated mice receiving saline pretreatment exhibited elevated ketone, creatinine and kidney weight ratios, representative of nephrotoxicity. Vitamin C and sodium bicarbonate lowered creatinine/ketone levels and kidney weight ratio whereas resveratrol normalized creatinine levels and kidney weight ratios similar to saline pretreatment. All pretreatments were associated with decreased ketone levels compared to saline pretreatment. Cisplatin-induced neuropathy (i.e. mechanical and cold allodynia) developed equivalently in all pretreatment groups and was similarly reversed by either morphine (6 mg/kg i.p.) or ibuprofen (6 mg/kg i.p.) treatment. RT-PCR showed that mRNA levels for IL-1β were increased in lumbar spinal cord of cisplatin-treated groups pretreated with either saline, NaHCO₃ or resveratrol/cisplatin-treated groups. However, IL-6 and TNF-alpha were elevated in the kidneys in all cisplatin-treated groups. Our studies also demonstrate that 60 days after the last cisplatin treatment, body weight, body temperature, kidney functions and mRNA levels have returned to baseline although the neuropathic pain (mechanical and cold) is maintained.

Conclusions

Studies employing cisplatin should include NaHCO₃ or vitamin C pretreatment to improve animal health status and reduce nephrotoxicity (lower creatinine and kidney weight ratio) without affecting the development of chemotherapy-induced neuropathy or analgesic efficacy.

Mechanism of action of indomethacin in indomethacin-responsive headaches

Indomethacin, as a member of the non-steroidal anti-inflammatory drug class, plays a special role in the treatment of headaches. By definition, it is completely efficacious in the treatment of the primary headache disorders paroxysmal hemicrania and hemicrania continua. Therefore, indomethacin is also used as a tool for differential diagnosis in headache clinics. Indomethacin has a clear action as a cyclooxygenase inhibitor. Additional mechanisms and interactions with cell signaling pathways and inflammatory pathways are considered in this article. However, it is not known what mechanism or interaction with pathophysiological mechanisms is the key to indomethacin's specific pharmacology in headache therapy. Focusing on headache therapy, we summarize the current knowledge of pharmacology, treatment options, and recommendations for the use of indomethacin in primary headaches. New findings from the field of headache research, as well as from Alzheimer's disease and cancer research on the pharmacological actions of indomethacin and their potential implications on the pathophysiology of indomethacin sensitive headaches, are discussed.

Differential involvement of mitochondrial dysfunction, cytochrome P450 activity, and active transport in the toxicity of structurally related NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of pain and inflammation. However, this group of drugs is associated with serious adverse drug reactions. Previously, we studied the mechanisms underlying toxicity of the NSAID diclofenac using Saccharomycescerevisiae as model system. We identified the involvement of several mitochondrial proteins, a transporter and cytochrome P450 activity in diclofenac toxicity. In this study, we investigated if these processes are also involved in the toxicity of other NSAIDs. We divided the NSAIDs into three classes based on their toxicity mechanisms. Class I consists of diclofenac, indomethacin and ketoprofen. Mitochondrial respiration and reactive oxygen species (ROS) play a major role in the toxicity of this class. Metabolism by cytochrome P450s further increases their toxicity, while ABC-transporters decrease the toxicity. Mitochondria and oxidative metabolism also contribute to toxicity of class II drugs ibuprofen and naproxen, but another cellular target dominates their toxicity. Interestingly, ibuprofen was the only NSAID that was unable to induce upregulation of the multidrug resistance response. The class III NSAIDs sulindac, ketorolac and zomepirac were relatively non-toxic in yeast. In conclusion, we demonstrate the use of yeast to investigate the mechanisms underlying the toxicity of structurally related drugs.

Modulation of glioma risk and progression by dietary nutrients and antiinflammatory agents

Gliomas are tumors of glial origin formed in the central nervous system and exhibit profound morphological and genetic heterogeneity. The etiology of this heterogeneity involves an interaction between genetic alterations and environmental risk factors. Scientific evidence suggests that certain natural dietary components, such as phytoestrogens, flavonoids, polyunsaturated fatty acids, and vitamins, may exert a protective effect against gliomas by changing the nature of the interaction between genetics and environment. Similarly, certain antiinflammatory drugs and dietary modifications, such as methionine restriction and the adoption of low-calorie or ketogenic diets, may take advantage of glioma and normal glial cells' differential requirements for glucose, methionine, and ketone bodies and may, therefore, be effective as part of preventive or treatment strategies for gliomas. Treatment trials of glioma patients and chemoprevention trials of individuals with a known genetic predisposition to glioma using the most promising of these agents, such as the antiinflammatory drugs curcumin and gamma-linolenic acid, are needed to validate or refute these agents' putative role in gliomas.

Evaluation of indomethacin and dexamethasone effects on BCRP-mediated drug resistance in MCF-7 parental and resistant cell lines

Breast cancer resistance protein is a member of the ATP-binding cassette transporter G family that extrudes xenotoxins from cells, mediating drug resistance, and has been recognized as a major cause of failure of various carcinoma chemotherapies. In this study, the modulatory effects of dexamethasone and indomethacin on the cell cytotoxicity of mitoxantrone and on the BCRP protein activity in breast cancer cell lines were examined. MCF cells were seeded at 1 x 10(4) cells per well in 96-well flat-bottomed microplates for 48 hours and treated with increasing doses of dexamethasone, indomethacin, and novobiocin alone or preincubated with increasing doses of the drugs and then coexposed to mitoxantrone. Cell viability was measured after 1-4 days, using the MTT assay. BCRP activity was determined flow cytometrically by measuring mitoxantrone accumulation in the absence and presence of the inhibitor, novobiocin. Cotreatment of mitoxantrone with different concentrations of dexamethasone and indomethacin sensitized parental and resistant MCF-7 cells to mitoxantrone cytotoxicity. Dexamethasone increased the accumulation of mitoxantrone in the MCF-7/MX cell line, indicating an inhibition of BCRP. In spite of increased levels of mitoxantrone cytotoxicity in the presence of indomethacin, the accumulation of mitoxantrone was not increased in indomethacin-treated MCF cells.

Celecoxib inhibits MDR1 expression through COX-2-dependent mechanism in human hepatocellular carcinoma (HepG2) cell line

The role of COX-2 in the regulation of the expression of MDR1, a P-glycoprotein involved in hepatocellular carcinoma cell line, HepG2, was studied in the present investigation. Celecoxib, a selective inhibitor of COX-2, at 25 microM concentration increased the accumulation of doxorubicin in HepG2 cells and enhanced the sensitivity of the cells to doxorubicin by tenfold. The induction of MDR1 expression by PGE2 and its downregulation by celecoxib or by COX-2 knockdown suggests that the enhanced sensitivity of HepG2 cells to doxorubicin by celecoxib is mediated by the downregulation of MDR1 expression, through COX-2-dependent mechanism. Further studies revealed the involvement of AP-1 in the celecoxib-induced downregulation of MDR1 expression. These experimental studies correlated well with in silico predictions and further suggested the inactivation of the signal transduction pathways involving ERK, JNK and p38. The present study thus demonstrates the usefulness of COX-2 intervention in overcoming the drug resistance in HepG2 cells.

Enhancement of doxorubicin cytotoxicity on human esophageal squamous cell carcinoma cells by indomethacin and 4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide (SC236) via inhibiting P-glycoprotein activity

Doxorubicin is a chemotherapeutic drug widely used for the treatment of advanced esophageal squamous cell carcinoma. However, its efficacy is usually limited by the development of multidrug resistance (MDR), which has been linked to the up-regulation of P-glycoprotein (P-gp) in cancer cells. Conventional nonsteroidal anti-inflammatory drugs and cyclooxygenase 2 (COX-2)-selective inhibitors have been demonstrated to overcome MDR in some cancer cells. Here we sought to elucidate the effect of COX inhibitors on doxorubicin-induced cytotoxicity in relation to P-gp function in human esophageal squamous cell carcinoma cells. Among the five tested COX inhibitors [indomethacin, 4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-benzenesulfonamide (SC236), 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluorom-ethylpyrazole (SC560), nimesulide, and N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS398)], all of which substantially suppressed prostaglandin E(2) (PGE(2)) production to a similar extent, only the nonselective COX inhibitor indomethacin and the COX-2-selective inhibitor SC236 enhanced cytotoxic effects of doxorubicin on HKESC-1 and HKESC-2 cells. Moreover, these effects could not be reversed by the addition of PGE(2). Knockdown of COX-2 by small interference RNA also failed to mimic the enhancing effects of indomethacin or SC236, implicating that their action is COX- and PGE(2)-independent. To this end, we observed that indomethacin and SC236 directly functioned as noncompetitive inhibitors of P-gp, which were manifested as a reduction of P-gp ATPase activity. Collectively, these findings suggest that the direct inhibitory effects of indomethacin and SC236 on P-gp may contribute to their ability to increase the intracellular retention of doxorubicin and thus enhance its cytotoxicity. The combination of indomethacin or SC236 with doxorubicin may have significant potential clinical application, especially in the circumvention of P-gp-mediated MDR in cancer cells.

Indomethacin overcomes doxorubicin resistance by decreasing intracellular content of glutathione and its conjugates with decreasing expression of gamma-glutamylcysteine synthetase via promoter activity in doxorubicin-resistant leukemia cells

Drug resistance continues to be a serious problem in cancer therapy. We investigated whether indomethacin, which inhibits cyclooxygenases, is able to overcome doxorubicin resistance in K562/ADR leukemia cells. Indomethacin at 10 microM increased the cytotoxicity of doxorubicin and vincristine in K562/ADR cells. Intracellular glutathione content was elevated in K562/ADR cells. Indomethacin treatment decreased glutathione content and glutathione-conjugates in K562/ADR cells. Increased expression of gamma-glutamylcysteine synthetase (gamma-GCS) was observed in K562/ADR cells, but this expression was decreased by indomethacin treatment. The activity of the gamma-GCS promoter from K562/ADR cells decreased after indomethacin treatment in MDA231 cells. These data strongly suggest that the cyclooxygenase inhibitor indomethacin increases the cytotoxicity of doxorubicin by decreasing the intracellular contents of glutathione and its conjugates with decreasing expression of gamma-GCS by inhibiting gamma-GCS promoter activity.

Indomethacin induces apoptosis via a MRP1-dependent mechanism in doxorubicin-resistant small-cell lung cancer cells overexpressing MRP1

Small-cell lung cancers (SCLCs) initially respond to chemotherapy, but are often resistant at recurrence. The non-steroidal anti-inflammatory drug indomethacin is an inhibitor of multidrug resistance protein 1 (MRP1) function. The doxorubicin-resistant MRP1-overexpressing human SCLC cell line GLC(4)-Adr was highly sensitive for indomethacin compared with the parental doxorubicin-sensitive line GLC(4). The purpose of this study was to analyse the relationship between hypersensitivity to indomethacin and MRP1 overexpression. The experimental design involved analysis of the effect of MRP1 downregulation on indomethacin-induced cell survival and apoptosis in GLC(4)-Adr and GLC(4), using siRNA. In addition the effect of indomethacin on glutathione levels and mitochondrial membrane potential was investigated. Small interfering RNAs directed against MRP1 reduced MRP1 mRNA levels twofold and reduced efflux pump function of MRP1, which was reflected by a 1.8-fold higher accumulation of MRP1 substrate carboxyfluorescein, in si-MRP1 versus si-Luciferase-transfected GLC(4)-Adr cells. Multidrug resistance protein 1 downregulation decreased initial high apoptosis levels 2-fold in GLC(4)-Adr after indomethacin treatment for 24 h, and increased cell survival (IC(50)) from 22.8+/-2.6 to 30.4+/-5.1 microM following continuous indomethacin exposure. Multidrug resistance protein 1 downregulation had no effect on apoptosis in GLC(4) or on glutathione levels in both lines. Although indomethacin (20 microM) for 2 h decreased glutathione levels by 31.5% in GLC(4)-Adr, complete depletion of cellular glutathione by L-buthionine (S,R)-sulphoximine only resulted in a small increase in indomethacin-induced apoptosis in GLC(4)-Adr, demonstrating that a reduced cellular glutathione level is not the primary cause of indomethacin-induced apoptosis. Indomethacin exposure decreased mitochondrial membrane potential in GLC(4)-Adr cells, suggesting activation of the mitochondrial apoptosis pathway. Indomethacin induces apoptosis in a doxorubicin-resistant SCLC cell line through an MRP1-dependent mechanism. This may have implications for the treatment of patients with MRP1-overexpressing tumours.

Cyclooxygenase in the treatment of glioma: its complex role in signal transduction

BACKGROUND

High-grade glioma remains one of the most difficult cancers to treat. Recent studies in oncology have identified a role of the ubiquitous enzyme, cyclooxygenase (Cox), especially cyclooxygenase-2 (COX-2) in cell proliferation, and its inhibition in cancer control, apoptosis, as well as synergy with other forms of therapy. The inhibitors of the Cox enzyme are well known as members of the nonsteroidal anti-inflammatory drug (NSAID) class of pharmaceuticals.

METHODS

In vitro and in vivo studies of different cancers expressing COX-2, including glioma studies, along with the few clinical trials that have been reported are reviewed to specifically identify the actions of these agents.

RESULTS

The anticancer effect of the COX-2 inhibitors may occur irrelevant of COX-2 expression, and it appears to be drug-specific, as well as dose-specific in different cancers. In combination with chemotherapeutic agents, the COX-2 inhibitors may have an additive, synergistic, or inhibitory effect on tumor growth.

CONCLUSIONS

As evaluations of this class of drugs begin in glioma, in vitro and in vivo data should be acquired to accurately predict which compounds will have an effect in controlling tumor growth and at which doses these should be used. The actual expression and inhibition of COX-2 may not always be relevant to the effects on tumor growth.

Synthesis of 2-methyl-3-indolylacetic derivatives as anti-inflammatory agents that inhibit preferentially cyclooxygenase 1 without gastric damage

Novel substituted 2-methyl-3-indolylacetic derivatives were synthesized and evaluated for their activity in vitro and in vivo on COX-1 and COX-2. Active compounds were screened to determine their gastrointestinal tolerability in vivo in the rat. Results showed that 3 and 4 preferentially inhibited COX-1 in vitro and in vivo. MD simulations indicated an induced fit for COX-1 but not for COX-2, probably because of a lower plasticity of the latter.

Celecoxib enhances doxorubicin-induced cytotoxicity in MDA-MB231 cells by NF-κB-mediated increase of intracellular doxorubicin accumulation

Non-steroidal anti-inflammatory drugs (NSAIDs) and cyclo-oxygenase (COX) inhibitors are anti-inflammatory agents that have also shown to be useful in anticancer therapy. In the present study, we show that the specific COX-2 inhibitor celecoxib enhances the inhibitory effect of doxorubicin (dox) on human MDA-MB231 breast tumour growth in vivo and in vitro. We also found that celecoxib increased the intracellular accumulation and retention of dox in vitro. Since the NSAID indomethacin and the specific COX-2 inhibitor NS398 did not affect the in vitro actions of dox, these effects are likely to be mediated via a COX-independent mechanism. It has been suggested that some COX-inhibitors can enhance the actions of cytostatics by overcoming multidrug resistance through the inhibition of ABC-transporter proteins. However, we found that the three main ATP-binding cassette (ABC)-transporter proteins, implicated in dox transport, were inactive in MDA-MB231 cells. Therefore, the finding that the P-glycoprotein (P-gp) blocker PSC833 also increased cellular accumulation of dox was unexpected. In order to unravel the molecular mechanisms involved in dox accumulation, we examined the involvement of NF-kappaB, as this transcription factor has been implicated in celecoxib action as well as in chemoresistance. We found that celecoxib and PSC833, but not indomethacin or NS398, almost completely inhibited basal- and dox induced NF-kappaB gene-reporter activity and p65 subunit nuclear translocation. Furthermore, the NF-kappaB inhibitor PDTC mimicked the actions of celecoxib and PSC833 on cell growth and on intracellular accumulation of dox, suggesting that NF-kappaB is functionally involved in the actions of these compounds. In conclusion, we show that structurally different compounds, among which are celecoxib and PSC833, increase the intracellular accumulation of dox and enhance dox induced cytotoxicity in MDA-MB231 breast cancer cells most likely via the modulation of NF-kappaB activity.

A phase I clinical and pharmacokinetic study of the multi-drug resistance protein-1 (MRP-1) inhibitor sulindac, in combination with epirubicin in patients with advanced cancer

PURPOSE

Multi-drug resistance mediated by ATP-binding cassette trans-membrane protein pumps is an important cause of cancer treatment failure. Sulindac has been shown to be a competitive substrate for the clinically important resistance protein, multi-drug resistance protein-1 (MRP-1), and thus might enhance the anti-cancer activity of substrate chemotherapeutic agents, e.g. anthracyclines.

METHODS

We conducted a dose-escalating, single arm, prospective, open label, non-randomised phase I trial of epirubicin (75 mg/m(2)) in combination with escalating oral doses of sulindac (0-800 mg) in patients with advanced cancer to identify an appropriate dose of sulindac to use in future resistance studies. Anthracycline and sulindac pharmacokinetics were studied in cycles 1 and 3.

RESULTS

Seventeen patients (8 breast, 3 lung, 2 bowel, 1 melanoma, 1 renal, 1 ovarian and 1 of unknown primary origin, 16/17 having had prior chemotherapy) were enrolled. Eight patients received a full six cycles of treatment; 14 patients received three or more cycles. Dose-limiting toxicity was observed in two patients at 800 mg sulindac (1 renal impairment, 1 fatal haemoptysis in a patient with advanced lung cancer), and sulindac 600 mg was deemed to be the maximum tolerated dose. Sulindac had no effect on epirubicin pharmacokinetics. Among 15 patients with evaluable tumour, two partial responses were seen (malignant melanoma and breast cancer). Four others had prolonged stable disease.

CONCLUSION

Epirubicin 75 mg/m(2) and sulindac 600 mg are the recommended doses for phase II studies for these agents in combination.

Distribution and functional activity of P-glycoprotein and multidrug resistance-associated proteins in human brain microvascular endothelial cells in hippocampal sclerosis

Multidrug resistance protein, also referred as P-glycoprotein (P-gp, MDR1; ABCB1) and multidrug resistance-associated protein (MRP) 1 (ABCC1) and 2 (ABCC2) are, thus far, candidates to cause antiepileptic drug (AED) resistance epilepsy. In this study, we investigated P-gp, MRP1 and MRP2 expression, localization and functional activity on cryosections and isolated human brain-derived microvascular endothelial cells (HBMEC) from epileptic patients (HBMEC-EPI) with hippocampal sclerosis (HS), as compared with HBMEC isolated from normal brain cortex (HBMEC-CTR). We examined the expression and distribution of three transporters, P-gp, MRP1 and MRP2 on two major parts of the resected tissue, the hippocampus and the parahippocampal gyrus (Gph). P-gp showed diffuse expression not only in endothelium but also by parenchymal cells in both the hippocampus and the Gph. MRP1 labeling was observed in parenchymal cells in the Gph. By contrast, MRP2 was mainly found in endothelium of the hippocampus. P-gp and MRP1 expression in the Gph was relatively high in the patient with long-term seizure history. Quantitative RT-PCR analysis of HBMEC revealed that MDR1, MRP1 as well as MRP5 (ABCC5) and MRP6 (ABCC6) were overexpressed in HBMEC-EPI at the mRNA level. HBMEC from both normal and epilepsy groups displayed protein expression of P-gp, whereas MRP1 and MRP2 were seen only in HBMEC-EPI. Accordingly, it is of particular interest that MRP functional activities were observed in HBMEC-EPI, but not in HBMEC-CTR. Our results suggest that complex MDR expression changes not only in the hippocampus but in the Gph may play a role in AED pharmacoresistance in intractable epilepsy patients with mesial temporal lobe epilepsy (MTLE) by altering the permeability of AEDs across the blood-brain barrier (BBB).

5-(4-Chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole acts in a reactive oxygen species-dependent manner to suppress human lung cancer growth

PURPOSE

5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) is a structural analog of celecoxib. Recent studies suggested that SC-560 inhibits the in vivo proliferation of colon and breast cancer cells to an extent similar to that observed in celecoxib, and that SC-560 exerts their growth inhibitory effects in a cyclooxygenase-independent manner.

METHODS

In the current study, we sought to investigate the mechanism by which SC-560 inhibits the growth of human lung cancer cells.

RESULTS

SC-560 more potently inhibited the growth of human A549, H460, and H358 lung cancer cell lines compared with that of human BEAS-2B normal bronchial epithelial cells. SC-560-induced growth inhibition was mainly due to the induction of cell-cycle arrest at the G1 phase without apoptosis induction. SC-560 rapidly and dose-dependently induced the generation of reactive oxygen species (ROS), followed by accumulation of cells at the G1 phase. Antioxidant pretreatment blocked the cell-cycle arrest and growth inhibition induced by SC-560. Combination treatment with other ROS-inducing agents such as alpha-tocopheryl succinate (TOS) augmented cellular response against SC-560, leading to synergistic apoptosis induction and growth suppression. Our data also showed that the apoptosis induced by combination treatment with SC-560 and TOS was mediated through ROS-dependent caspase activation.

CONCLUSION

Collectively, our results demonstrate that SC-560 acts in a ROS-dependent manner to induce growth suppression in human lung cancer cells.

Indomethacin overcomes doxorubicin resistance with inhibiting multi-drug resistance protein 1 (MRP1)

Drug resistance continues to be a serious problem in cancer therapy. We investigated whether indomethacin, which inhibited cyclooxygenases, would overcome doxorubicin resistance in K562/ADR leukemia cells. Indomethacin at 10 muM increased the cytotoxicity of doxorubicin, as well as vincristine in K562/ADR. Both multi-drug resistant protein1 (MRP1) and P-glycoprotein were overexpressed in K562/ADR cells when compared with K562 parent cells (K562/P). Expression of MRP1 mRNA and protein, but not P-glycoprotein, was significantly decreased in K562/ADR cells after indomethacin treatment. Indomethacin treatment increased 5(6)-carboxyfluorescein diacetate (CFDA) efflux, as well as decreased accumulation in K562/ADR cells. The activity of the MRP1 promoter decreased after indomethacin treatment in Hela cells. These data strongly suggest that the cyclooxygenase inhibitor, indomethacin, increased the cytotoxicity of doxorubicin with decreasing expression of MRP1 through inhibition of MRP1 promoter activity.

Altered expression of topoisomerase IIalpha contributes to cross-resistant to etoposide K562/MX2 cell line by aberrant methylation

KRN 8602 (MX2) is a novel morpholino anthracycline derivative having the chemical structure 3′-deamino-3′-morpholino-13-deoxo-10-hydroxycarminomycin hydrochloride. To investigate the mechanisms of resistance to MX2, we established an MX2-resistant phenotype (K562/MX2) of the human myelogeneous leukaemia cell line (K562/P), by continuously exposing a suspension culture to increasing concentrations of MX2. K562/MX2 cells were more resistant to MX2 than the parent cells, and also showed cross-resistance to etoposide and doxorubicin. Topoisomerase (Topo) IIα protein levels in K562/MX2 cells were lower of those in K562/P cells on immunoblot analysis and decreased expression of Topo IIα mRNA was seen in K562/MX2 cells. Topoisomerase II catalytic activity was also reduced in the nuclear extracts from K562/MX2 cells when compared with K562/P cells. Aberrant methylated CpG of Topo IIα gene was observed in K562/MX2 cells when compared with the parent line on methylation-specific restriction enzyme analysis. To overcome the drug resistance to MX2 and etoposide, we investigated treatment with 5-Aza-2′-deoxycytidine (5AZ), which is a demethylating agent, in K562/MX2 cells. 5-Aza-2′-deoxycytidine treatment increased Topo IIα mRNA expression in K562/MX2 cells, but not in K562/P cells, and increased the cytotoxicity of MX2 and etoposide. Methylated CpG was decreased in K562/MX2 cells after 5AZ treatment. We concluded that the mechanism of drug resistance to MX2 and etoposide in K562/MX2 cells might be the combination of decreased expression of Topo IIα gene and increased methylation, and that 5AZ could prove to be a novel treatment for etoposide-resistant cell lines, such as K562/MX2.

Modulation of MRP-1-mediated multidrug resistance by indomethacin analogues

Multidrug resistance (MDR) is a major limiting factor in the development and application of drug candidates. MDR caused by MRP-1 is known to be modulated by the nonsteroidal antiinflammatory drug indomethacin. We have synthesized and biologically evaluated a library of indomethacin analogues. The indomethacin-derived compound library was synthesized employing the Fischer-indole synthesis as the key transformation and making use of a "resin-capture-release" strategy. Sixty representative members of the library were evaluated in a cell biological cytotoxicity assay employing the MRP-1 expressing human glioblastoma cell line T98G as a model system. Nine of the 60 tested derivatives increased the doxorubicin-mediated cytotoxicity at a comparable or higher level than indomethacin itself. Analysis of these derivatives revealed an interesting structure-function relationship. Most remarkably, two substances increased the toxicity, when doxorubicin was used at clinically relevant low concentrations, at a higher degree than indomethacin.

Inhibition of cell invasion by indomethacin on glioma cell lines: in vitro study

Malignant glioma invasion into the surrounding brain tissue is still a major problem for any therapeutical methods. Matrix metalloproteinases (MMPs) have been implicated as important factors in this pathological process. In this study, one of the non-steroidal anti-inflammatory drugs (NSAIDs) indomethacin was employed to investigate the effect of inhibition of cell invasion mediated by MMP-2 and MMP-9 in human malignant glioma cell lines, A172, U87MG, U251MG, and U373MG in vitro. MTT assay was firstly examined to determine non-cytotoxic dose range, then gelatin zymography, matrigel invasion assay, migration assay and MMP-2 activity assay for 24 h exposure in indomethacin were employed to assess the inhibitory effect of indomethacin. MTT assay revealed that dose with 0, 50, and 500 microM/ml were non-cytotoxic. Zymography demonstrated: (a) expression of MMP-2 and MMP-9 activity was downregulated along with elevated dose of indomethacin. (b) MMP-2 activity that changed from pro-MMP-2 to active form of MMP-2 in supernatants of cell lines could not be inhibited by indomethacin. Invasion assay disclosed that the number of invading cells through the matrigel were significantly decreased in a dose dependent manner. Migration assay indicated indomethacin did not affect cells migration. MMP-2 activity assay showed the total and active MMP-2 secretion was suppressed by 500 microM/ml of indomethacin. Our present study is the first report on inhibitive effect of indomethacin mediated by MMP-2 and MMP-9 in invasion assay of glioma cell lines. The current study suggested that non-cytotoxic level of indomethacin was able to reduce the cell invasion of malignant gliomas mediated by MMP-2 and MMP-9, but it did not affected on cell motility. It also lowered down the activity of MMP-2 and MMP-9, and could reduce of MMP-2 secretion of cell lines. Thus, high concentration of indomethacin within non-cytotoxic dose might offer a new therapeutic strategy to impair cell invasion of gliomas.

Potentiation by alpha-tocopheryl succinate of the etoposide response in multidrug resistance protein 1-expressing glioblastoma cells

Multidrug resistance protein 1 (MRP1) is one of the representative members of the ATP-binding cassette superfamily of transporters that is involved in resistance to chemotherapeutic agents in cancer patients. MRP1 functions as an efflux pump of drugs, primarily those conjugated to glutathione (GSH). Decreases in the intracellular concentration of GSH have been shown to enhance the response of MRP1-overexpressing cells to MRP1-substrate drugs by limiting the available drug-GSH conjugates. We report here that alpha-tocopheryl succinate (TOS), a vitamin E analogue, decreased intracellular GSH concentration and blocked MRP1 function in glioblastoma cells. Functional blockade by TOS of MRP1 was confirmed by the enhanced accumulation of etoposide (VP-16), an MRP1-substrate drug. As a result, co-treatment of TOS with VP-16 or treatment with liposomes containing both TOS and VP-16 greatly enhanced the response of MRP1-expressing glioblastoma cells to VP-16. TOS may be a promising adjuvant for enhancing the therapeutic efficacy of VP-16 in patients with MRP1-expressing glioblastomas.

Multidrug resistance-associated protein MRP1 expression in human gliomas: chemosensitization to vincristine and etoposide by indomethacin in human glioma cell lines overexpressing MRP1

The 190 kDa multidrug resistance protein MRP1 is likely to be involved in the multidrug resistance phenotype of human gliomas. MRP1 expression was evaluated in surgical tumor samples from 17 patients with gliomas. In addition, the impact of the MRP's inhibitor, indomethacin, on the chemosensitivity to etoposide (VP16) and vincristine (VCR) of two glioblastoma cell lines expressing MRP1 (GL15 and 8MG) was investigated. When evaluated in tumor samples, MRP1 expression was observed in all of them with more than 90% of stained tumor cells in 14/15 high-grade gliomas. MRP1 was also strongly expressed at the membrane of the vascular endothelial cells in the same 14 tumor samples, suggesting that the permeability to anticancer drugs could be also limited across brain tumor vessels. At concentrations comprised between 5 and 50 microM, indomethacin significantly increased the cytotoxic effect of etoposide in both cell lines but it was more efficient in increasing the cytotoxicity of VCR on GL15 cells, as compared with 8MG cells. These results suggest that the association of indomethacin to VCR or etoposide could be of interest in the clinical management of gliomas.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

P-glycoprotein and multidrug resistance-associated protein mediate specific patterns of multidrug resistance in malignant glioma cell lines, but not in primary glioma cells

Understanding and overcoming multidrug resistance (MDR) may be a promising strategy to develop more effective pharmacotherapies for malignant gliomas. In the present study, human malignant glioma cell lines (n=12) exhibited heterogeneous mRNA and protein expression and functional activity of the mdr gene-encoded P-glycoprotein (PGP) and MDR-associated protein (MRP). Correlation between mRNA expression, protein levels and functional activity was strong. Inhibition of PGP activity by verapamil or PSC 833 enhanced the cytotoxic effects of vincristine, doxorubicin, teniposide and taxol. Inhibition of MRP activity by indomethacin or probenecid enhanced the cytotoxic effects of vincristine, doxorubicin and teniposide. The human cerebral endothelial cell line, SV-HCEC, exhibited the strongest PGP activity of all cell lines. Five primary human glioblastomas and one anaplastic astrocytoma displayed heterogenous protein levels of PGP and MRP-1 in tumor cells and of PGP in biopsy specimens in vivo, but no functional activity of these proteins upon ex vivo culturing. These data suggest that the glioma cell line-associated MDR-type drug resistance is a result of long-term culturing and that cerebral endothelial, but not glioma cells, may contribute to MDR-type drug resistance of gliomas in vivo.

Aspirin and indomethacin exhibit antiproliferative effects and induce apoptosis in T98G human glioblastoma cells

The in vitro antiproliferative and apoptosis inducing properties of the nonsteroidal anti-inflammatory drugs (NSAIDs) like acetyl salicylic acid (aspirin) and indomethacin were investigated in T98G human glioblastoma cells to explore their potential role in the chemoprevention of human glioma. The biological effects induced by aspirin and indomethacin on T98G cells, in which the expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were confirmed by RT-PCR and immunostaining, were investigated by studying cell proliferation and apoptosis assays. The antiproliferative effects occurred in a dose- and time-dependent manner on T98G cells by the treatment with 0.1 -2 mM aspirin and 25-100 microM indomethacin. Moreover, aspirin displayed the greatest growth inhibition within 24 h. Approximately 90% growth inhibition occurred following treatment either with 2 mM aspirin or 100 microM indomethacin by 72 h and induction of apoptosis was confirmed by DNA laddering and TUNEL assay. Our in vitro findings indicate that aspirin and indomethacin have an antiproliferative effect on T98G human glioblastoma cells at toxic concentrations.

Structure-activity relationship of indomethacin analogues for MRP-1, COX-1 and COX-2 inhibition. identification of novel chemotherapeutic drug resistance modulators

We report the screening of analogues of indomethacin to investigate the structure-activity relationship (SAR) of indomethacin-mediated multidrug resistance associated protein-1 (MRP-1) inhibition. By examining the activities of compounds with minor variations of the parent structure, we were able to separate MRP-1, glutathione-S-transferase (GST), cyclooxygenase (COX)-1 and COX-2 inhibitory activities. Combination cytotoxicity assays were utilised to identify agents which possess synergistic potential in MRP-1-expressing cell lines. MRP-1 Inside Out Vesicles (IOVs) were utilised to demonstrate the ability of the indomethacin analogues to inhibit the pump directly. Most of the indomethacin analogues active as MRP-1 inhibitors were poor GST inhibitors when compared with the GST-inhibitory activity of indomethacin. Two of the MRP-1 inhibitory analogues were found to have no COX-1 inhibitory activity and low COX-2 inhibitory activity, suggesting potentially reduced clinical toxicity. One MRP-1 inhibitory indomethacin analogue was also found to have low COX-1 inhibitory activity, but significant COX-2 inhibitory activity, making this analogue again interesting in terms of low potential toxicity, but with the possibility of direct inhibitory effects on tumour growth.

Persistent accumulation of cyclooxygenase-1-expressing microglial cells and macrophages and transient upregulation by endothelium in human brain injury

OBJECT

Secondary damage after central nervous system (CNS) injury is driven in part by oxidative stress and CNS inflammation and is substantially mediated by cyclooxygenases (COXs). To date, the rapidly inducible COX-2 isoform has been primarily linked to inflammatory processes, whereas expression of COX-1 is confined to physiological functions. The authors report the differential localization of COX-1 in human traumatic brain injury (TBI).

METHODS

Differential cellular COX-1 protein expression profiles were analyzed following TBI in 31 patients and compared with neuropathologically unaltered control brains by using immunohistochemistry. In these patients with TBI, a significant increase of COX-1 protein expression by vessel endothelial and smooth-muscle cells and CD68+ microglia/macrophages was observed to be strictly confined to the lesion. Accumulation of COX-1+ microglia/macrophages in the lesion was already evident 6 hours postinjury, reaching maximal levels after several weeks and remaining elevated at submaximal levels for several months after injury. Furthermore, COX-1+ cell clusters were located in the Virchow-Robin space during the leukocyte infiltration period from Days 4 to 8 after TBI. Double-labeling experiments confirmed coexpression of COX-1 by CD68+ microglia/macrophages. The numbers of COX-1+ vessel endothelial and smooth-muscle cells increased from Day 1, remaining at submaximal levels for months after injury.

CONCLUSIONS

The prolonged accumulation of COX- 1+ microglia/macrophages that were restricted to perilesional areas affected by the acute inflammatory response points to a role of COX-1 in secondary injury. The authors have identified localized, accumulated COX- I expression as a potential pharmacological target following TBI. Their results challenge the current paradigms of a selective COX-2 role in the postinjury inflammatory response.

Cloning and characterization of the rat multidrug resistance-associated protein 1

Multidrug resistance-associated protein 1 (MRP1) was originally shown to confer resistance of human tumor cells to a broad range of natural product anticancer drugs. MRP1 has also been shown to mediate efflux transport of glutathione and glucuronide conjugates of drugs and endogenous substrates. An ortholog of MRP1 in the mouse has been cloned and characterized. Significant functional differences between murine and human MRP1 have been noted. Since drug disposition and pharmacology studies often are conducted in rats, there is a need to clone and characterize the rat ortholog of MRP1. We isolated a rat MRP1 (rMRP1) cDNA from rat brain astrocytes, characterized its coding sequences, and verified the transport activity of the protein expressed in MRP1 cDNA-transfected Madin-Darby canine kidney (MDCK) cells. Our results showed that rMRP1 has a coding sequence of 4599 bp, which predicts a polypeptide of 1533 amino acids with an apparent molecular weight of 190 kd by Western immunoblot analysis. rMRP1-transfected MDCK cells are capable of efflux transport of a fluorescent MRP1 marker - calcein - that is inhibitable by known MRP1 inhibitors, indomethacin, and MK571. Sequence analysis indicates that rMRP1 is more closely related to mouse MRP1 than human MRP1.

Traumatic brain injury induces prolonged accumulation of cyclooxygenase-1 expressing microglia/brain macrophages in rats

Inflammatory cellular responses to brain injury are promoted by proinflammatory messengers. Cyclooxygenases (prostaglandin endoperoxide H synthases [PGH]) are key enzymes in the conversion of arachidonic acid into prostanoids, which mediate immunomodulation, mitogenesis, apoptosis, blood flow, secondary injury (lipid peroxygenation), and inflammation. Here, we report COX-1 expression following brain injury. In control brains, COX-1 expression was localized rarely to brain microglia/macrophages. One to 5 days after injury, we observed a highly significant (p < 0.0001) increase in COX-1+ microglia/macrophages at perilesional areas and in the developing core with a delayed culmination of cell accumulation at day 7, correlating with phagocytic activity. There, cell numbers remained persistently elevated up to 21 days following injury. Further, COX-1+ cells were located in perivascular Virchow-Robin spaces also reaching maximal numbers at day 7. Lesion-confined COX-1+ vessels increased in numbers from day 1, reaching the maximum at days 5-7. Double-labeling experiments confirmed coexpression of COX-1 by ED-1+ and OX-42+ microglia/ macrophages. Transiently after injury, most COX-1+ microglia/macrophages coexpress the activation antigen OX-6 (MHC class II). However, the prolonged accumulation of COX-1+, ED-1+ microglia/macrophages in lesional areas enduring the acute postinjury inflammatory response points to a role of COX-1 in the pathophysiology of secondary injury. We have identified localized, accumulated COX-1 expression as a potential pharmacological target in the treatment of brain injury. Our results suggest that therapeutic approaches based on long-term blocking including COX-1, might be superior to selective COX-2 blocking to suppress the local synthesis of prostanoids.

Synthesis of indomethacin analogues for evaluation as modulators of MRP activity

Synthesis of a range of indomethacin analogues, required for investigation in combination toxicity assays, bearing both N-benzyl and N-benzoyl groups, is described.

Persistent accumulation of cyclooxygenase-1 (COX-1) expressing microglia/macrophages and upregulation by endothelium following spinal cord injury

Acute inflammation following spinal cord injury results in secondary injury and pathological reorganisation of the central nervous system (CNS) architecture. Cyclooxygenases (Prostaglandin Endoperoxide H Synthases, PGH) are key enzymes in the conversion of arachidonic acid into prostanoids which mediate immunomodulation, mitogenesis, apoptosis, blood flow, secondary injury (lipid peroxygenation) and inflammation. Here, we report cyclooxygenase-1 (COX-1) expression following spinal cord injury. In control spinal cords, COX-1 expression was localized by immunohistochemistry to ependymal cells, some neurons, inclusive dorsal and ventral root ganglion cells, few endothelial cells but rarely to brain microglia/macrophages. In injured spinal cords, COX-1(+) microglia/macrophages accumulated highly significantly (P<0.0001) at peri-lesional areas and in the developing necrotic core early after injury. Here numbers of COX-1(+) cells remained persistently elevated up to 4 weeks following injury. Further, COX-1(+) cells were located in perivascular Virchow-Robin spaces, between spared axons and in areas of Wallerian degeneration. Double labeling experiments confirmed co-expression of COX-1 by ED-1(+) and OX-42(+) microglia/macrophages. Transiently after infarction most COX-1(+) microglia/macrophages coexpress the activation antigen OX-6 (MHC class II). However, the prolonged accumulation of COX-1(+) microglia/macrophages at the lesion site enduring the acute post injury inflammatory response points to a role of COX-1 in tissue remodeling or secondary injury. We have identified and localized persistent accumulation of COX-1 expressing cells which might be a potential pharmacological target following spinal cord injury. Therefore, we suggest that approaches based on: (i) short-term; and (ii) selective COX-2 blocking alone might not be a sufficient tool to suppress the local synthesis of prostanoids.