Cyclooxygenase Type 2 Expression Research Articles

Vitamin D, linoleic acid, arachidonic acid and COX-2 in colorectal cancer patients in relation to disease stage, tumour localisation and disease progression

Background and study aimsEvidence shows that vitamin D and cyclooxygenase type 2 (COX-2) might play role in aetiology/progression of cancer. It is suggested that antitumour effect of vitamin D depends on vitamin D-receptor (VDR) expression. Aim of the study was to determine vitamin D and polyunsaturated fatty acids in colorectal cancer patients. Patients and methodsA total of 39 patients with colorectal cancer (mean ± SD age: 65.5 ± 6.8 years) and 25 controls (mean ± SD age: 51.0 ± 6.9 years) were studied. 25-hydroxycholecalciferol-25(OH)D3 in serum was quantitatively determined by high-performance liquid chromatography (HPLC). Levels of linoleic acid (LA) and arachidonic acid (AA) of serum phospholipids were measured by gas-chromatography (GC). Expression of VDR and COX-2 in normal colonic mucosa and tumour tissue was measured by real time polymerase chain reaction (RT-PCR). ResultsThe mean value of 25(OH)D3 was significantly lower in the colorectal cancer patients with early stages of the disease and in patients with tumour confined to the rectum compared to control group (p < 0.02, p < 0.03, respectively). The higher concentration of AA (patients with early stages of the disease) and lower concentration of LA (patients with the advanced stages of the disease) was noticed compared to the control group. For the patients with the early stages of the disease the higher mean fold change of mRNA VDR and the lower mean fold change of mRNA COX-2 was noticed (p < 0.03, p < 0.02, respectively). ConclusionThe assessment of vitamin D status in patients with colorectal cancer should include measurement of mRNA VDR expression in tumour tissue.

Chronic administration of sildenafil improves endothelial function in spontaneously hypertensive rats by decreasing COX-2 expression and oxidative stress

AimsSpontaneously hypertensive rats (SHR) exhibit impaired endothelial vasodilation and enhanced vasoconstriction. The phosphodiesterase 5 (PDE5) inhibitor sildenafil (Sild) potentiates the nitric oxide (NO)-mediated effects exerting antioxidative and anti-inflammatory actions. In the present study, we hypothesized that Sild could improve endothelial function in SHR. Materials and methodsMale rats were treated daily for 60 days by oral gavage with Sild (45 mg/kg) before the onset of the hypertensive state (pre-hypertensive protocol). The aortic relaxation to acetylcholine (ACh), sodium nitroprusside (SNP) and the phenylephrine (Phe)-induced contraction was evaluated in SHR. Protein expression of eNOS, p-eNOS, caveolin, COX-1, COX-2, ERK and p-ERK was measured by Western blot. Key findingsResting blood pressure was not modified by Sild administration. Treatment with Sild did not alter the relaxation response to SNP but improved the ACh-induced relaxation and reduced Phe-induced contraction in aortic rings from SHR. This protective effect of Sild could be attributed to reduced superoxide anions (O2−) generation, cyclooxygenase type 2 (COX-2) protein downregulation and increased NO bioavailability. SignificanceSild improves endothelial function in SHR aorta without affecting resting blood pressure values. These results indicate that PDE5 inhibition has a potential role in the improvement of vascular function and could be an adjuvant in the treatment of essential hypertension.

Cyclooxygenase-2 expression and its association with vascular endothelial growth factor, microvessel density and clinicopathologic characteristics of colorectal carcinoma

The aim of this study was to investigate the expression of cyclooxygenase type-2 (COX-2) and its association with angiogenesis and clinicopathologic characteristics of colorectal carcinoma (CRC). COX-2 expression was detected by means of immunohistochemistry in a series of human tissue samples with CRC (n = 120), dysplasia tissue closely adjacent to carcinomas (n = 40) and normal colorectal mucosa (n = 40), and their expressions association with vascular endothelial growth factor (VEGF), CD31-labeled micorvessel density(MVD) in CRC and other clinicopathologic characteristics were investigated. The expression of COX-2 in CRC tissues (78.3%) was obviously higher than that in adjacent tissue and normal mucosal tissue (p&lt;0.01). COX-2 expression was correlated significantly with the grading, advanced cancer, Dukes stage and lymph node metastasis, distant metastasis and VEGF (p&lt;0.05). Our result demonstrates that COX-2 expression was significantly higher in earlier stages of CRC. It can be suggested that COX-2 expression may be important in the initial development of CRC. The findings of the present study suggest that COX-2 overexpression in CRC may be considered as a negative prognostic marker.

Chitosan/siRNA nanoparticles targeting cyclooxygenase type 2 attenuate unilateral ureteral obstruction-induced kidney injury in mice.

Cyclooxygenase type 2 (COX-2) plays a predominant role in the progression of kidney injury in obstructive nephropathy. The aim of this study was to test the efficacy of chitosan/small interfering RNA (siRNA) nanoparticles to knockdown COX-2 specifically in macrophages to prevent kidney injury induced by unilateral ureteral obstruction (UUO). Using optical imaging techniques and confocal microscopy, we demonstrated that chitosan/siRNA nanoparticles accumulated in macrophages in the obstructed kidney. Consistent with the imaging data, the obstructed kidney contained a higher amount of siRNA and macrophages. Chitosan-formulated siRNA against COX-2 was evaluated on RAW macrophages demonstrating reduced COX-2 expression and activity after LPS stimulation. Injection of COX-2 chitosan/siRNA nanoparticles in mice subjected to three-day UUO diminished the UUO-induced COX-2 expression. Likewise, macrophages in the obstructed kidney had reduced COX-2 immunoreactivity, and histological examination showed lesser tubular damage in COX-2 siRNA-treated UUO mice. Parenchymal inflammation, assessed by tumor necrosis factor-alpha (TNF-α) and interleukin 6 mRNA expression, was attenuated by COX-2 siRNA. Furthermore, treatment with COX-2 siRNA reduced heme oxygenase-1 and cleaved caspase-3 in UUO mice, indicating lesser oxidative stress and apoptosis. Our results demonstrate a novel strategy to prevent UUO-induced kidney damage by using chitosan/siRNA nanoparticles to knockdown COX-2 specifically in macrophages.

Regulation of miR-101/miR-199a-3p by the epithelial sodium channel during embryo implantation: involvement of CREB phosphorylation.

In our previous study, we have demonstrated that the epithelial sodium channel (ENaC) mediates the embryo-derived signals leading to the activation of CREB and upregulation of cyclooxygenase type 2 (COX2) required for embryo implantation. This study aims to investigate whether microRNAs (miRNAs) are involved in the ENaC-induced upregulation of COX2 during embryo implantation. The results show that the levels of miR-101 and miR-199a-3p, two COX2 targeting miRNAs, are reduced by ENaC activation, and increased by ENaC inhibition or knock-down of ENaC subunit (ENaCα) in human endometrial surface epithelial (HES) cells or in mouse uteri during implantation. Phosphorylation of CREB is induced by the activation of ENaC, and blocked by ENaC inhibition or knockdown in HES cells. Knockdown of ENaCα or CREB in HES cells or in mouse uterus in vivo results in increases in miR-101 and miR-199a-3p, accompanied with decreases in COX2 protein levels and reduction in implantation rate. The downregulation of COX2 caused by knockdown of ENaC or CREB can be recovered by the inhibitors of miR-101 or miR-199a-3p in HES cells. These results reveal a novel molecular mechanism modulating COX2 expression during embryo implantation via ENaC-dependent CREB activation and COX2-targeting miRNAs.

Long-lasting oxidative pulmonary insult in rat after intratracheal instillation of silica nanoparticles doped with cadmium

Silica/cadmium containing nanomaterials are now produced on industrial scale due to their potential for a variety of technological applications. Nevertheless, information on toxicity, exposure and health impact of these nanomaterials is still limited. In this study, in vivo effects of silica nanoparticles (SiNPs) doped with Cd (SiNPs-Cd, 1mg/rat), soluble CdCl2 (400μg/rat), or SiNPs (600μg/rat) have been investigated by evaluating F2-isoprostanes (F2-IsoPs), superoxide dismutase (SOD1), inducible nitric oxide synthase (iNOS) and cyclooxygenase type 2 (COX-2) enzymes, as markers of oxidative stress, 24h, 7 and 30 days after intra-tracheal (i.t.) instillation to rats. Free and esterified F2-IsoPs were evaluated in lung and plasma samples by GC/NICI-MS/MS analysis, and SOD1, iNOS and COX-2 expression in pulmonary tissue by immunocytochemistry.Thirty days after exposure, pulmonary total F2-IsoPs were increased by 56% and 43% in CdCl2 and SiNPs-Cd groups, respectively, compared to controls (32.8±7.8ng/g). Parallel elevation of free F2-IsoPs was observed in plasma samples (by 113% and 95% in CdCl2 and SiNPs-Cd groups, respectively), compared to controls (28±8pg/ml). These effects were already detectable at day 7 and lasted until day 30 post-exposure. Pulmonary SOD1-, iNOS-, and COX-2-immunoreactivity was significantly enhanced in a time-dependent manner (7 days <30 days) after both CdCl2 and SiNPs-Cd treatments. SiNPs did not influence any of the evaluated endpoints.The results indicate the capacity of engineered SiNPs-Cd to cause long-lasting oxidative tissue injury following pulmonary exposure in rat.

Disruption of cyclooxygenase-2 prevents downregulation of cortical AQP2 and AQP3 in response to bilateral ureteral obstruction in the mouse

Bilateral ureteral obstruction (BUO) in rats is associated with increased cyclooxygenase type 2 (COX-2) expression, and selective COX-2 inhibition prevents downregulation of aquaporins (AQPs) in response to BUO. It was hypothesized that a murine model would display similar changes in renal COX-2 and AQPs upon BUO and that targeted disruption of COX-2 protects against BUO-induced suppression of collecting duct AQPs. COX-2(-/-) and wild-type littermates (C57BL/6) were employed to determine COX-1, -2, AQP2, and AQP3 protein abundances and localization after BUO. In a separate series, sham and BUO wild-type mice were treated with a selective COX-2 inhibitor, parecoxib. The COX-2 protein level increased in wild-type mice in response to BUO and was not detectable in COX-2(-/-). COX-1 protein abundance was increased in sham-operated and BUO mice. Total AQP2 and -3 mRNA and protein levels decreased significantly after BUO in the cortex+outer medulla (C+OM) and inner medulla (IM). The decrease in C+OM AQP2 and -3 levels was attenuated/prevented in COX-2(-/-) mice, whereas there was no change in the IM. In parallel, inhibition of COX-2 by parecoxib rescued C+OM AQP3 and IM AQP2 protein level in wild-type mice subjected to BUO. In summary, 1) In C57BL/6 mice, ureteral obstruction increases renal COX-2 expression in interstitial cells and lowers AQP2/-3 abundance and 2) inhibition of COX-2 activity by targeted disruption or pharmacological blockade attenuates obstruction-induced AQP downregulation. In conclusion, COX-2-derived prostaglandins contribute to downregulation of transcellular water transporters in the collecting duct and likely to postobstruction diureses in the mouse.

Plasma levels of vascular endothelial growth factor during and after radiotherapy in combination with celecoxib in patients with advanced head and neck cancer

Celebrex and radiotherapy in advanced head and neck cancer. This phase I dose-escalation study seeks to determine the phase II recommended dose of cyclooxygenase type 2 (COX-2) inhibitor in patients with locally advanced squamous cell head and neck (H&N) cancer, treated with accelerated radiotherapy. Anti-vasculogenic effect of this treatment on serum vascular endothelial growth factor (VEGF) is examined. Patients were irradiated with curative intent (72Gy in 6weeks). Celecoxib was administered throughout the radiotherapy course. Serum VEGF level were tested during radiotherapy and in follow-up. Tumor specimens were stained to quantify the COX-2 expression. Thirty-two patients completed the treatment. The dose of celecoxib was escalated (200, 400 and 800mg bid, then de-escalated to 600mg bid). The acute toxicity related to the treatment in the first and second cohort did not reach grade III; in the third cohort three patients had grade III radiation toxicity and one had celecoxib-related toxicity. In the last fourth cohort the toxicity was acceptable. Significant VEGF level drop (p=0.011) was found between radiation day 1 and post-treatment visit. Significant decrease (p=0.022) of the VEGF level was shown in patients with high COX-2 expression in the tumor. Phase II recommended dose of celecoxib combined with accelerated radiotherapy in advanced H&N cancer was 600mg bid. A significant decrease of the post-treatment serum VEGF level compared to the initial level was noticed only in patients with high COX-2 expression in tumors.

Increased cyclooxygenase-2 expression and prostaglandin E2production in pressurized renal medullary interstitial cells

Renal medullary interstitial cells (RMICs) are subjected to osmotic, inflammatory, and mechanical stress as a result of ureteral obstruction, which may influence the expression and activity of cyclooxygenase type 2 (COX-2). Inflammatory stress strongly induces COX-2 in RMICs. To explore the direct effect of mechanical stress on the expression and activity of COX-2, cultured RMICs were subjected to varying amounts of pressure over time using a novel pressure apparatus. COX-2 mRNA and protein were induced following 60 mmHg pressure for 4 and 6 h, respectively. COX-1 mRNA and protein levels were unchanged. PGE(2) production in the RMICs was increased when cells were subjected to 60 mmHg pressure for 6 h and was prevented by a selective COX-2 inhibitor. Pharmacological inhibition indicating that pressure-induced COX-2 expression is dependent on p38 MAPK and biochemical knockdown experiments showed that NF-kappaB might be involved in the COX-2 induction by pressure. Importantly, terminal deoxyneucleotidyl transferase-mediated dUTP nick-end labeling and methylthiazoletetetrazolium assay studies showed that subjecting RMICs to 60 mmHg pressure for 6 h does not affect cell viability, apoptosis, and proliferation. To further examine the regulation of COX-2 in vivo, rats were subjected to unilateral ureteral obstruction (UUO) for 6 and 12 h. COX-2 mRNA and protein level was increased in inner medulla in response to 6- and 12-h UUO. COX-1 mRNA and protein levels were unchanged. These findings suggest that in vitro application of pressure recapitulates the effects on RMICs found after in vivo UUO. This directly implicates pressure as an important regulator of renal COX-2 expression.

Cyclo-oxygenase type 2 is dysregulated in breast ductal carcinoma in situ and correlates with poor outcome

Objective Clinico-pathologic data on microinvasive carcinoma of the breast (MICB) as defined by the 2003 TNM criteria (T1mic ≤ 1 mm) are scarce. Nowadays, we do not know the percentages of Ductal Carcinoma in situ (DCIS) that will progress to invasion and predictive markers are not available. Cyclo-oxygenase type-2 (COX-2) is overexpressed in many human malignant tumours and has been linked to the processes of carcinogenesis, cell survival, invasion and metastasis. Despite the data on elevated COX-2 expression in breast neoplasia, the mechanism of upregulation remains unclear. This study aims to evaluate COX-2 expression in DCIS in comparison to MICB in order to establish the importance of this marker as a predictor of microinvasion and the correlation with Van Nuys classification. Study design A retrospective study was performed on archival paraffin-embedded formalin-fixed tissue samples of DCIS and MICB from women who had undergone surgery. The COX-2 expression was assayed by immunohistochemistry using a specific polyclonal anti-human COX-2 antibody. Expression was scored in a scale 0 (absent) to 4 (strong) based on the extent and intensity of tumour cell staining. Results Fifty-two cases of DCIS and 40 of MICB were studied. In all cases, COX-2 was detected in the cytoplasm of tumour cells, and elevated COX-2 expression was observed in Van Nuys high-grade CDIS cases compared with low and intermediate grades ( p < 0.05). In addition, enhanced COX-2 expression was significantly higher in DCIS component from MICB patients (82% cases) than in DCIS pure patients (40.4%) ( p < 0.05). In a multivariate model which includes age, tumour size, mammography, histological grade and COX-2 expression, we found COX-2 positivity to be an independent factor for microinvasion (OR 3.90; 95% CI 1.88–14.3). Conclusions COX-2 is associated to higher Van Nuys grades of breast CDIS, and could be a molecular marker to identify the cases of DCIS which could progress to MICB. Condensation COX-2 as a molecular marker in microinvasive carcinoma of the breast.

Effect of 17-α hydroxyprogesterone caproate on the production of tumor necrosis factor-α and the expression of cyclooxygenase-2 in lipopolysaccharide-treated gravid human myometrial explants

To determine whether 17-alpha hydroxyprogesterone (17-OHPC) alters tumor necrosis factor-alpha (TNF-alpha) production and the expression of cyclooxygenase type 2 (COX-2) in myometrium exposed to lipopolysaccharide (LPS). Lower segment myometrial biopsies were obtained from non-laboring patients at term. Tissues were cultured in serum-free media with 17-OHPC (1 microM) and LPS (1 microg/ml), either alone or in combination. At 24 h, the production of tumor necrosis factor-alpha (TNF-alpha) and the expression of COX-2 was determined using enzyme linked immunosorbent assay and real-time (RT-PCR). Statistical analysis was performed using non-parametric testing. A P-value of <0.05 was considered significant. 17-OHPC had no effect on TNF-alpha production and COX-2 expression when compared with untreated myometrial explants (P=0.61 and P=0.95). LPS induced production of TNF-alpha (P=0.03) and expression of COX-2 (P=0.02). Treatment with 17-OHPC did not block LPS-induced TNF-alpha production (P=0.37) or COX-2 expression (P=0.12). In this pilot study, 17-OHPC did not affect the production of TNF-alpha or COX-2 expression in human myometrium.

Prognostic significance of tumor iNOS and COX-2 in stage III malignant cutaneous melanoma.

New prognostic markers are needed for malignant melanoma. Inducible nitric oxide synthase (iNOS) and cyclooxygenase type 2 (COX-2) have been described to correlate with progression of melanoma. Moreover, activating mutations in BRAF/NRAS oncogenes are often detected in melanoma. The BRAF/NRAS mutation status and expression of COX-2 and iNOS were examined to compare their prognostic value for overall survival (OS) in stage III malignant cutaneous melanoma. The expression of iNOS and COX-2 in metastatic lymph nodes from 21 rapidly progressing (OS from date of diagnosis of stage III disease < or =14 months) and 17 slowly progressing (OS > or =60 months) stage III cutaneous melanoma patients was examined by immunohistochemistry. The presence of BRAF/NRAS mutations was analyzed using direct DNA sequencing. Chi2 exact trend test and logistic regression analysis were used for statistical analysis. Both iNOS (P = 0.002) and COX-2 (P = 0.048) alone significantly predicted OS. The BRAF/NRAS mutation status did not significantly differ between patient groups, although iNOS significantly (P = 0.013) correlated with BRAF mutation frequency. Furthermore, the odds ratio (OR) with respect to OS of iNOS (OR = 10.4) was higher than that of COX-2 (OR = 5.6) and was stable in the multivariate analysis of OS together with disease stage IIIB/C, ulceration, number of metastatic lymph nodes, and Breslow tumor thickness. Our data show that iNOS is an independent and stronger prognostic factor for OS in stage III malignant cutaneous melanoma than COX-2.

Evaluation of [11C]rofecoxib as PET tracer for cyclooxygenase 2 overexpression in rat models of inflammation

Overexpression of cyclooxygenase type 2 (COX-2) is triggered by inflammatory stimuli, but it also plays a prominent role in the initiation and progression of various diseases. This study aims to investigate [(11)C]rofecoxib as a positron emission tomography (PET) tracer for COX-2 expression. [(11)C]Rofecoxib was prepared by methylation of its sulphinate precursor. Regional brain distribution and specific binding of [(11)C]rofecoxib in healthy rats was studied by ex vivo biodistribution and autoradiography. Regional brain distribution and PET imaging studies were also performed on rats with severe encephalitis, caused by nasal infection with herpes simplex virus (HSV). Finally, ex vivo biodistribution and blocking studies were carried in rats with a sterile inflammation, induced by intramuscular turpentine injection. [(11)C]rofecoxib brain uptake in control animals corresponded with the known distribution of COX-2. Pretreatment with NS398 significantly reduced tracer uptake in the cingulate/frontopolar cortex, whereas the reduction in hippocampus approached significance. Ex vivo autoradiography also revealed preferential tracer uptake in hippocampus and cortical areas that could be blocked by NS398. In HSV-infected animals, [(11)C]rofecoxib uptake was moderately increased in all brain regions, but it could not be blocked with indomethacin. Yet, some PET images revealed increased tracer uptake in brain areas with microglia activation. In turpentine-injected animals, [(11)C]rofecoxib uptake in inflamed muscle was not higher than in control muscle and could not be blocked with NS398. Indomethacin caused a slight reduction in muscle uptake. Despite the apparent correlation between [(11)C]rofecoxib uptake and COX-2 distribution in healthy rats, [(11)C]rofecoxib could not unambiguously detect COX-2 overexpression in two rat models of inflammation.

COX2 in a euryhaline teleost,Fundulus heteroclitus: primary sequence, distribution, localization, and potential function in gills during salinity acclimation

In the kidneys of mammals, cyclooxygenase type 2 (COX2) is expressed in medullary interstitial cells, the macula densa and epithelial cells of the cortical thick ascending limb where it generates prostaglandins that regulate hormone secretion, inhibit ion transport, and support cell survival during salt loading and dehydration. In teleosts, the gills are in direct contact with an aquatic environment and are the dominant site of osmoregulation. During transfers between salinities, specialized cells in the gills (chloride cells) rapidly regulate NaCl secretion for systemic osmoregulation while they simultaneously are exposed to acute osmotic shock. This study was conducted to determine if COX2 is expressed in the gills, and if so, to evaluate its function in cellular and systemic osmoregulation. Degenerate primers, reverse transcription-PCR and rapid amplification of cDNA ends were used to deduce the complete cDNA sequence of a putative COX2 enzyme from the gills of the euryhaline killifish (Fundulus heteroclitus). The 2,738 base pair cDNA includes a coding region for a 610 amino acid protein that is over 70% identical to mammalian COX2. A purified antibody generated against a conserved region of mouse COX2 labeled chloride cells, suggesting that the enzyme may control NaCl secretion as an autocrine agent. Real-time PCR was then used to demonstrate that mRNA expression of the COX2 homologue was threefold greater in gills from chronic seawater killifish than in gills from chronic freshwater killifish. Expression of Na(+)/K(+)/2Cl(-) cotransporter and the cystic fibrosis transmembrane conductance regulator were also greater in seawater, suggesting that chronic COX2 expression in the gills is regulated in parallel to the key ion transporters that mediate NaCl secretion. Real-time PCR was also used to demonstrate that acute transfer from seawater to freshwater and from freshwater to seawater led to rapid, transient inductions of COX2 expression. Together with previous physiological evidence, the present molecular and immunological data suggest that constitutive branchial COX2 expression is enhanced in seawater, where prostaglandins can regulate NaCl secretion in chloride cells. Our data also suggest that branchial COX2 expression may play a role in cell survival during acute osmotic shock.

Immune modulatory effects of cyclooxygenase type 2 inhibitors in HIV patients on combination antiretroviral treatment

To examine the immune modulating effects of cyclooxygenase type 2 (COX-2) inhibitors (COX-2i) in HIV-infected patients on combination antiretroviral treatment (CART). In-depth substudy from an approved, open, controlled, randomized study comparing the immune modulating effects of CART in combination with COX-2i after 12 weeks. Patients (n = 38) on long-term CART with stable viral load (VL) < 50,000 copies/ml and CD4+ T-cell counts > 100/microl were randomized to CART and rofecoxib 25 mg bid (n = 12) or celecoxib 400 mg bid (n = 12), or CART only without placebo (n = 14). Routine clinical chemistry, CD4+ and CD8+ counts and VL were safety parameters. Immunological parameters included C-reactive protein, beta2-microglobulin, Ig isotypes and IgG subclasses as well as several T-lymphocyte subsets. Non-parametric analyses were used throughout. Prestudy experiments showed higher median intracellular expression of COX-2 in CD4+ (P = 0.048) and possibly CD8+ (P = 0.09) T cells from patients on CART compared with uninfected controls. In the clinical study, increased CD4+ T-cell counts were observed only in patients on COX-2i with VL < 50 copies/ml (P = 0.02). Decreased expression of CD38+ on CD8+ T cells and subsets as well as reductions in IgA and IgM (P < 0.03) were most pronounced in patients on COX-2i who had detectable VL (n = 6). COX-2i treatment enhanced the perforin content particularly in the differentiated CD27-/CD8+ T-cell subsets compared with controls (P = 0.05). COX-2i together with CART improved markers for persistent immune activation, particularly in patients with viraemia, as well as enhanced perforin expression, and thereby strengthened COX-2 as a potential therapeutic target in HIV infection.

COX-2 and neurodegeneration in Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Recent observations link cyclooxygenase type-2 (COX-2) to the progression of the disease. Consistent with this notion, studies with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) show that inhibition and ablation of COX-2 markedly reduce the deleterious effects of this toxin on the nigrostriatal pathway. The similarity between this experimental model and PD strongly supports the possibility that COX-2 expression is also pathogenic in PD.

Expression of cyclooxygenase type 2 in lepromatous and tuberculoid leprosy lesions

Leprosy is an infectious disease with two polar forms, tuberculoid leprosy (TL) and lepromatous leprosy (LL), which are dominated by T-helper (Th) 1 and Th2 cells, respectively. High concentrations of prostaglandin E2 produced by the inducible enzyme cyclooxygenase type 2 (COX-2) in LL could inhibit Th1 cytokine production, contributing to T-cell anergy. To compare the COX-2 expression in LL and TL. Skin biopsies from 40 leprosy patients (LL, n = 20; TL, n = 20) were used to determine by immunohistochemistry and automated morphometry the percentage of COX-2 immunostained cells. Most COX-2-positive cells were macrophages; their percentages in the inflammatory infiltrate located in the papillary dermis, reticular dermis and periadnexally were significantly higher in LL than TL (P < 0.001 by Student's t-test). The high expression of COX-2 in LL may be related to high prostaglandin production contributing to T-cell anergy.

Hyaluronan-induced cyclooxygenase-2 expression promotes thromboxane A2 production by renal cells

Matrix degradation products such as fragmented hyaluronan (HA) display important proinflammatory effects on renal tubular epithelial cells (TECs) and macrophages (MPhis). We hypothesized that HA could up-regulate cyclooxygenase type 2 (COX-2) in these cells and that the subsequent production of thromboxane A2 (TXA2) could play a role in inflammatory renal lesions. We used an in vitro approach to examine the expression of COX-1 and COX-2 and the production of TXA2 in response to fragments of HA. COX-2 mRNA, protein, and the resulting TXA2 production were measured in CD44-positive, HA-responsive cells lines of TECs and MPhi. COX-2 mRNA was also measured in vivo in MRL-Faslpr mice and in mice with anti-glomerular basement membrane (anti-GBM) nephritis. In TECs and MPhis, HA increased the steady-state COX-2 mRNA and protein levels markedly, whereas COX-1 mRNA levels did not change. The HA-induced response was comparable to lipopolysaccharide stimulation. In comparison with MPhi, the response was much weaker in TECs. Likewise, the production of TXA2 in response to HA was markedly increased in MPhi, but less in TECs. In TECs and in MPhi, the HA-stimulated TXA2 synthesis was inhibited with the COX-2-selective inhibitors SC58125 (12.5 micromol/L) or celecoxib (0.25 to 5.00 micromol/L). COX-2 mRNA levels were increased in nephritic mice with MRL-Faslpr lupus nephritis and in mice with anti-GBM disease. HA is a proinflammatory factor that stimulates COX-2 expression and subsequent TXA2 production. Since HA accumulates markedly in renal injury, we speculate that this matrix molecule could therefore play a significant role in thromboxane-mediated immune events in the kidney.

Apoptosis Induced by gp120 in the Neocortex of Rat Involves Enhanced Expression of Cyclooxygenase Type 2 and Is Prevented by NMDA Receptor Antagonists and by the 21-Aminosteroid U-74389G

The effects of a single dose of the HIV-1 coat protein gp120 given into one lateral cerebral ventricle (i.c.v.) on the expression of cyclooxygenase type 2 (COX-2) and PGE2 levels have been studied using Western blotting and ELISA techniques applied to brain tissue extracts obtained from the neocortex of individual rats, one of the regions of the central nervous system where the viral protein causes apoptosis. The results demonstrate that COX-2 expression is almost doubled 6 h after a single dose (100 ng) of gp120 and this is paralleled by a statistically significant elevation of PGE2. Enhanced COX-2 expression is implicated in the mechanisms of apoptosis evoked by gp120 because the latter is prevented by NS398 (10 mg/kg i.p.), a selective inhibitor of COX-2 activity. Protection is also afforded by NMDA receptor antagonists, such as MK801 (0.3 mg/kg i.p.) and CGP040116 (10 mg/kg i.p.), and by the free radical scavenger, U-74389G (10 mg/kg i.p.), supporting a glutamate-mediated, excitotoxic, mechanism of apoptotic death induced by gp120. These data together with the observation that MK801 failed to prevent gp120-enhanced COX-2 expression indicate that products of the arachidonic cascade may be responsible for elevation of synaptic glutamate leading neocortical cells to oxidative stress and excitotoxic apoptosis.

HIV-1 gp120-induced apoptosis in the rat neocortex involves enhanced expression of cyclo-oxygenase type 2 (COX-2).

The effect of subchronic intracerebroventricular (i.c.v.) injection of the human immunodeficiency virus type 1 (HIV-1) recombinant protein gp120 (100 ng, given daily for up to 7 consecutive days) on cyclooxygenase type 2 (COX-2) expression was studied by immunohistochemistry in the brain of adult rats. In comparison to control, bovine serum albumin (100 ng, given i.c.v. for up to 7 days) treated animals (n = 6), a single daily injection of the viral protein for 7 consecutive days enhanced the number of COX-2 immunoreactive cells in the brain cortex of rats (n = 6 per group) and this was accompanied by a 50% increase over control PGE2 content in whole brain tissue homogenates (n = 6). In another series of experiments, pretreatment of rats (n = 6) with indomethacin (6.0 mg/kg given i.p. 1 h before gp120 injection), an inhibitor COX activity, prevented apoptotic death typically produced by gp120 in the neocortex of rat suggesting that enhancement of COX-2 expression may be involved in the mechanisms of apoptosis yielded by the HIV-1 coat protein.