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Biomedical subjects

A J Knox

Publications and source records attributed to A J Knox.

At least 37 records · Page 2Linked to original sources
PubMed2000

Selectivity of cyclo-oxygenase inhibitors in human pulmonary epithelial and smooth muscle cells.

Cyclo-oxygenase (COX) inhibitors may have a role in reducing inflammation in asthma and other pulmonary diseases. COX inhibitors have different selectivities for the two COX isoenzymes (COX 1 and COX 2) which vary between purified enzyme and intact cell preparations. The relative selectivity of COX inhibitors has not been studied in human airway cells. A number of COX inhibitors in cultured human airway cells were compared which exclusively express either COX 1 (primary degree cultured human airway smooth muscle (HASM) cells) or COX 2 (A549 pulmonary epithelial cell-line) as measured by Western blotting. COX activity was assayed by prostaglandin (PG)E2 production following 30 min incubation with 5 mM arachidonic acid. COX activity in both cell types was similar; HASM cells 92.2+/-12.1 ng PGE2 x mg-1 protein, A549 cells 87.7+/-24.4 ng PGE2 mg-1 protein. In HASM cells the median inhibitory concentration (IC50) was >10-5 M for nimesulide, 3.2 x 10-6 M for N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulphonamide (NS398), 1.8 x 10-8 M for flurbiprofen, 6.7 x 10-9 M for indomethacin and >10-5 M for aspirin. In A549 cells the IC50 was 1.8 x 10-9M for nimesulide, 4.1 x 10-9 M for NS398,6.2 x 10-10 M for flurbiprofen, 1.3 x 10-8 M for indomethacin and >10-5 M for aspirin. Sodium valerate had no effect in either HASM or A549 cells. The COX 2:COX 1 selectivity ratio (COX 2 IC50/COX I IC50) was <0.0001 for nimesulide, 0.001 for NS398, 0.03 for flurbiprofen and 1.9 for indomethacin. In conclusion the present study has shown that cyclo-oxygenase inhibitors have a range of selectivities for cyclo-oxygenase 1 and cyclo-oxygenase 2 in intact human airway cells. The relative cyclo-oxygenase 2 selectivity of N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulphonamide and nimesulide may have implications for the treatment of asthma and other inflammatory pulmonary diseases.

Adult↗
PubMed2000

Questionnaire survey of male infertility in cystic fibrosis.

Most male cystic fibrosis (CF) patients are infertile due to obstructive azospermia but little is known about the best time to counsel patients on infertility. All male patients attending the Adult Nottingham CF unit were invited to complete an anonymous questionnaire on infertility. The response rate was 60%. The median age that the patients first became aware of male infertility was 17 years (range 13-24) but the preferred age of receiving this information was 14 years (range 8-16). Patients first learnt about male infertility from the CF team (six patients), parents (five), from written information (two) or unexpectedly (five). Five out of 18 patients had undergone seminal analysis at a median age of 26 years but 17/18 patients felt that this should be offered routinely. Our survey has shown that patients would like infertility discussions at a younger age and routine seminal analysis.

Adolescent↗
PubMed2000

Successful pregnancy and birth after IVF in a woman with cystic fibrosis.

As survival increases, patients with cystic fibrosis (CF) are often confronted with reproductive issues. Initial reports gave conflicting advice regarding the outcome of pregnancy in CF. However a recent large longitudinal study of pregnancies in CF women suggested that pregnancy has little impact on morbidity or mortality. Reduced fertility in CF women has been described, possibly due to thickened cervical mucus, and intrauterine insemination (IUI) has been used to overcome this. We report the first woman with CF, to our knowledge, to be successfully treated with IVF after repeated failed attempts at IUI.

Adult↗
PubMed2000

TGF-beta1 stimulates IL-8 release, COX-2 expression, and PGE(2) release in human airway smooth muscle cells.

We have recently shown that endogenous prostanoids are critical in bradykinin-stimulated interleukin (IL)-8 release from human airway smooth muscle (ASM) cells. In this study, we tested the ability of transforming growth factor (TGF)-beta1 to stimulate IL-8 release, cyclooxygenase (COX)-2 expression and PGE(2) generation in cultured human ASM cells and explored the role of COX products and COX-2 induction on IL-8 release. TGF-beta1 stimulated IL-8 release, COX-2 induction, and PGE(2) generation in a concentration- and time-dependent manner. Maximal IL-8 release was achieved with 10 ng/ml of TGF-beta1 after 16 h of incubation, which was inhibited by the transcription inhibitor actinomycin D and the corticosteroid dexamethasone but was not affected by the nonselective COX inhibitor indomethacin and the selective COX-2 inhibitor NS-398 despite their inhibition on TGF-beta1-induced PGE(2) release. These results show for the first time that TGF-beta1 stimulates IL-8 release, COX-2 induction, and PGE(2) generation in human ASM cells and that PGE(2) generation is not critical for TGF-beta1-induced IL-8 release. These findings suggest that TGF-beta1 may play an important role in the pathophysiology of asthma.

Aged↗
PubMed2000

Synergistic inhibition by beta(2)-agonists and corticosteroids on tumor necrosis factor-alpha-induced interleukin-8 release from cultured human airway smooth-muscle cells.

We have previously reported that human airway smooth-muscle (ASM) cells produce abundant interleukin (IL)-8, a major neutrophil chemoattractant involved in asthma exacerbations. Here, we tested the effects of the beta(2)-agonists salbutamol (Salbu) and salmeterol (Salme) on IL-8 release and tumor necrosis factor (TNF)-alpha-induced IL-8 release from ASM cells. We found that TNF-alpha strongly enhanced IL-8 release in a time- and concentration-dependent manner, whereas Salbu, Salme, the direct adenylyl cyclase activator forskolin (FSK), and the cyclic monophosphate (cAMP) analogue 8-bromoadenosine 3',5'-cAMP (8-Br-cAMP) alone weakly stimulated IL-8 release. TNF-alpha (10 ng/ml)-induced IL-8 release was markedly inhibited by the steroids dexamethasone (Dex) (0.1 to 10 microM) and fluticasone (Flut) (0.01 to 1 microM) but unaffected by Salbu, Salme, FSK, or 8-Br-cAMP. However, a combination of Dex (1 microM) or Flut (0.1 microM) with Salbu (10 microM), Salme (1 microM), FSK (10 microM), or 8-Br-cAMP (10 and 100 microM) significantly enhanced the inhibition by Dex or Flut alone. Experiments with KT5720, a selective inhibitor of cAMP-dependent protein kinase A; rolipram, a selective inhibitor of type IV phosphodiesterase; and ICI-118,551, a beta(2)-receptor antagonist, suggested that the synergistic inhibition was mediated by beta(2)-receptor in a cAMP-dependent manner. This novel synergistic interaction of beta(2)-agonists and steroids may partly explain the benefits that result when these agents are combined to treat asthma.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Targeting remodeling in respiratory inflammation.

Chronic asthma causes considerable morbidity, mortality and utilization of healthcare resources. The fact that asthma still causes such problems despite the widespread use of anti-inflammatory treatment suggests that new approaches are needed. Airways in chronic asthma are characterized by considerable remodeling which affects a number of structures, particularly airway smooth muscle and changes in airway smooth muscle thickness may be one of the most important determinants of bronchial hyperresponsiveness. Here we suggest new approaches that might be used to target smooth muscle remodeling in asthma.

Animals↗
PubMed1999

Mechanisms involved in desensitization of particulate guanylyl cyclase in human airway smooth muscle: the role of protein kinase C.

We recently showed that cultured human airway smooth muscle cells (HASMC) express both soluble and particulate guanylyl cyclases (GC) and that long term treatment with atrial natriuretic peptide (ANP) causes homologous desensitization of particulate GC. Here we determine if protein kinase C (PKC) activation would desensitize particulate GC and probe the role of PKC in particulate GC desensitization. Pretreatment of HASMC with phorbol 12-myristate 13-acetate (PMA), a PKC activator led to time and concentration-dependent desensitization of ANP-stimulated cGMP accumulation. GF109203X, a selective PKC inhibitor, blocked the PMA-induced desensitization, but did not block ANP-induced desensitization. In addition, desensitization by PMA and ANP showed an additive effect. These results suggest that PKC activation can desensitize particulate GC but that the desensitization induced by ANP is PKC-independent.

1-Methyl-3-isobutylxanthine↗
PubMed1999

The effect of topical benzamil and amiloride on nasal potential difference in cystic fibrosis.

The electrochemical defect in the bronchial epithelium in cystic fibrosis (CF) consists of defective chloride secretion and excessive sodium reabsorption. The sodium channel blocker, amiloride, has been shown to reversibly correct the sodium reabsorption in CF subjects, but long term studies of amiloride have been disappointing due to its short duration of action. Benzamil, a benzyl substituted amiloride analogue, has a longer duration of action than amiloride in cultured human nasal epithelium. The results of the first randomized, placebo controlled, double blind, crossover study are reported here comparing the effects of benzamil and amiloride on nasal potential difference (nasal PD) in CF. Ten adults with CF attended on three occasions. At each visit baseline nasal PD was recorded, the drug (amiloride 1 x 10(-3) M, benzamil 1.7 x 10(-3) M, or 0.9% sodium chloride) was administered topically via a nasal spray, and nasal PD was measured at 15, 30 min, 1, 2, 4 and 8 h. Results were expressed as maximum change in nasal PD from baseline (PDmax), time for PDmax to return to 50% of baseline (t0.5), and the area under the curve (AUC). PDmax values for benzamil (20.6+/-0.9 mV) and amiloride (20.3+/-1.6 mV), were similar. The duration of effect was much longer for benzamil as measured as either AUC or t0.5 AUC values were 11.8+/-1.6 mV for benzamil, 2.8+/-0.4 mV for amiloride and 0.6+/-0.4 mV for placebo. The AUC value for benzamil was significantly greater than amiloride (95% confidence interval (CI) for the difference 5.3-12.7 mV, p<0.0001). t0.5 values were 4.3+/-0.7 h for benzamil and 0.6+/-0.1 h for amiloride (95% CI for the difference 2.0-5.3 h, p<0.001). It is concluded that benzamil has a similar maximal effect to amiloride but a more prolonged duration of action on nasal potential difference in cystic fibrosis. Benzamil may be a useful sodium channel blocker for the long-term treatment of the biochemical defect in the lungs of patients with cystic fibrosis.

Administration, Intranasal↗
PubMed1999

The effect of the nitric oxide synthase inhibitor, L-NMMA, on sodium metabisulphite-induced bronchoconstriction and refractoriness in asthma.

Refractoriness to indirect bronchoconstrictor stimuli, is a feature of asthma but the mechanism is poorly understood. This study tested the hypothesis that endogenous nitric oxide (NO) produced during a first bronchoconstrictor challenge protects against subsequent challenge and therefore has a role in the refractory process. The effect of an NO synthase inhibitor, N(G)-mono-methyl-L-arginine (L-NMMA), on refractoriness to sodium metabisulphite (MBS) was investigated in 20 subjects with mild asthma. On visit one, the dose of MBS which caused a 20% fall in forced expiratory volume in one second (FEV1) (PD20) was determined. On visit two, the refractory index (RI) to MBS was determined by challenging the subjects twice with their PD20 of MBS, the second challenge proceeding after recovery from the first. Those showing a refractory index of approximately 30% (10 subjects) inhaled either L-NMMA or placebo followed 5 min later by two challenges with their PD20 of MBS in a double-blind cross over study at two further visits. The dose of L-NMMA used was shown to reduce exhaled NO for a duration sufficient to cover the second MBS challenge However, no significant difference was found between L-NMMA and placebo in maximum fall in FEV1% and area under the curve (AUC) during first or second MBS challenges or in RI on the two study days. It is concluded that subjects with mild asthma show refractoriness to sodium metabisulphite, but that endogenous nitric oxide is unlikely to be involved either in the refractory process or in the response to sodium metabisulphite per se.

Asthma↗
PubMed1999

Immunocytochemical localization of cyclo-oxygenase isoforms in cultured human airway structural cells.

BACKGROUND: Cyclo-oxygenase (COX) exists as two isoforms, COX-1, the constitutive isoform, and COX-2, which is inducible by cytokines or inflammatory stimuli and may participate in airway inflammation. OBJECTIVE: To determine the basal distribution of COX isoforms, and their regulation by interleukin-1 beta (IL-1beta), bradykinin (BK) and dexamethasone (Dex) in cultured airway structural cells. METHODS: We measured COX-1 and COX-2 in cultured human airway smooth muscle (HASM) cells, MRC5 fibroblasts and normal human epithelial cells (NHBE) using immunocytochemical analysis. RESULTS: The majority of all types of untreated cultured cells expressed COX-1 (75% of HASM, 75% of MRC5 fibroblasts and 72% of NHBE cells). Fibroblasts and smooth muscle cells showed low constitutive COX-2 expression (2 and 8%, respectively) but this was higher in NHBE cells (28%). IL-1beta (24 h incubation) or BK (4 h incubation) had no effect on COX-1 expression in any of the cells studied. In contrast, there was a two- and 1.5-fold rise in the percentage of NHBE cells expressing COX-2; a 7.5- and sixfold rise in the percentage of HASM cells expressing COX-2 and a 33.5- and 20.5-fold increase in the percentage of fibroblasts expressing COX-2 after IL-1beta or BK treatment, respectively. Pretreatment with dexamethasone abolished IL-1beta- and BK-stimulated COX-2 induction in all cells studied. CONCLUSION: COX-1 is expressed constitutively in human airway fibroblasts, smooth muscle and epithelial cells but epithelial cells also show constitutive expression of COX-2. Both IL-1beta and BK induced COX-2 expression in all cells studied and this induction was blocked by dexamethasone. Immunocytochemical techniques can be successfully used to detect the distribution of COX isoforms in cell cultures.

Blotting, Western↗
PubMed1999

Antiproliferative effects of NO and ANP in cultured human airway smooth muscle.

Airway smooth muscle (ASM) hypertrophy and hyperplasia are important determinants of bronchial responsiveness in asthma, and agents that interfere with these processes may prevent airway remodeling. We tested the hypothesis that activators of soluble and particulate guanylyl cyclases would inhibit human ASM cell (HASMC) proliferation. We report that the nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP; 10(-6) to 10(-4) M) and sodium nitroprusside (10(-5) to 10(-3) M) and human atrial natriuretic peptide [ANP-(1-28); 10(-8) to 10(-6) M], which activate soluble and particulate guanylyl cyclases, respectively, inhibited serum- and thrombin-induced proliferation of cultured HASMCs. The antimitogenic effect of SNAP was reversed by hemoglobin (10(-5) M), an NO scavenger, suggesting that NO donation was involved. The antiproliferative effects of SNAP and ANP-(1-28) were potentiated by the cGMP-specific phosphodiesterase zaprinast and mimicked by 8-bromo-cGMP (10(-6) to 10(-3) M), suggesting that cGMP-dependent mechanisms were involved. However, first, ANP-(1-28) produced a smaller antiproliferative effect than SNAP in contrast to their abilities to elevate cGMP, and second, rat ANP-(104-126), which binds selectively to ANP clearance receptors without elevating cGMP, had a small antiproliferative effect, suggesting that cGMP-independent mechanisms were also involved. These results provide evidence for a novel antiproliferative effect of NO and ANP in HASMCs mediated through cGMP-dependent and cGMP-independent mechanisms.

Asthma↗
PubMed1999

Desensitization of guanylyl cyclases in cultured human airway smooth-muscle cells.

We previously showed that cultured human airway smooth-muscle cells (HASMC) contain soluble and particulate guanylyl cyclases (GCs). We studied the desensitization of soluble and particulate GCs in HASMC. Homologous desensitization of soluble GC occurred after incubation with S-nitroso-N-acetyl pencillamine (SNAP). SNAP-dependent desensitization was blocked by hemoglobin, a nitric oxide (NO) scavenger, suggesting that it was due to NO release. Cross-desensitization between SNAP and sodium nitroprusside (SNP) and the lack of thiol reduction after SNAP or SNP treatment suggested that thiol depletion was not involved. Assays for soluble GC activity and experiments using protein synthesis inhibitors suggested that SNAP-dependent desensitization was due to reduced soluble GC. Homologous desensitization of particulate GC occurred after pretreatment with atrial natriuretic peptide (ANP) accompanied by reduced particulate GC activity. Recovery required protein synthesis, suggesting that it was due to reduction in particulate GC. Homologous desensitization to either SNAP or ANP was not altered by phosphodiesterase (PDE) inhibitors, suggesting that increased PDE activity was not involved. Cross-desensitization experiments using SNAP and ANP and experiments using zaprinast to elevate cyclic guanosine monophosphate showed no evidence of heterologous desensitization. Our results suggest that pretreatment of HASMC with SNAP or ANP causes homologous, but not heterologous, desensitization of soluble and particulate GCs, respectively.

Atrial Natriuretic Factor↗
PubMed1999

Treatment of pulmonary exacerbations of cystic fibrosis leads to improved antioxidant status.

Many cystic fibrosis (CF) patients have increased circulating levels of oxidation products and/or decreased antioxidant status. This study investigated whether treatment of pulmonary exacerbations decreased oxidative stress in CF patients. Seventeen adult patients were studied at the beginning and end of treatment with intravenous antibiotics. Plasma concentrations of the antioxidants ascorbic acid, alpha-tocopherol, uric acid and total reduced thiols, together with plasma retinol, lipid hydroperoxides, malondialdehyde and protein carbonyl levels were determined. Median (interquartile range) pretreatment and post-treatment levels were compared using the Wilcoxon signed rank test. Clinical resolution was reflected by improved spirometry. Significant increases were observed in plasma ascorbic acid (pre 30.4 (15.7-38.6) microM, post 35.2 (27.3-49.6) microM), alpha-tocopherol (pre 19.7 (13.6-25.2) microM, post 25.2 (19.3-31.6) microM) and retinol (pre 1.9 (1.5-2.5) microM, post 2.7 (1.7-3.5) microM). No change in plasma total reduced thiols occurred following treatment (pre 409 (366-420) microM, post 392 (366-423) microM), whereas uric acid fell with treatment (pre 307 (274-394) microM, post 260 (216-317) microM). Neither plasma protein carbonyls or malondialdehyde levels altered with treatment (protein carbonyls pre 0.47 (0.28-1.27), post 0.67 (0.42-0.83) nM x mg protein(-1); malondialdehyde pre 0.75 (0.53-1.18), post 0.84 (0.65-1.15) microM). Lipid hydroperoxides levels did decrease following treatment (53 (18-85) versus 17 (10-55) nM). This study demonstrated that treatment of infective exacerbations resulted in increased plasma levels of some antioxidant vitamins. No immediate change in plasma protein oxidation was observed, but lipid oxidation was decreased.

Adult↗
PubMed1998

Bradykinin stimulates IL-8 production in cultured human airway smooth muscle cells: role of cyclooxygenase products.

IL-8 is an important neutrophil and eosinophil chemoattractant in asthma. A recent report has suggested that bradykinin (BK), an asthmatic mediator, induces the release of IL-8 in nonairway cells. We have recently reported that BK causes cyclooxygenase (COX)-2 induction and PGE2 release in human airway smooth muscle (ASM) cells. In this study, we tested the ability of BK to induce IL-8 from these cells and explored the role of COX products and COX-2 induction in this process. Confluent serum-deprived human ASM cells were studied. IL-8 was assayed by specific ELISA. Unstimulated cells released low levels of IL-8. BK enhanced IL-8 release in a concentration- and time-dependent fashion (maximum 50-fold increase over basal). The nonselective COX inhibitor indomethacin and the selective COX-2 inhibitor NS-398 strongly inhibited BK-stimulated PGE2 and IL-8 production. The COX substrate arachidonic acid also caused PGE2 and IL-8 production, and its effect was inhibited by nonselective COX inhibitors but unaffected by NS-398. Both the BK- and arachidonic acid-induced IL-8 production was inhibited by the protein synthesis inhibitors cycloheximide and actinomycin D and by the steroid dexamethasone. Furthermore, exogenous PGE2 and calcium ionophore A23187 also stimulated IL-8 release. BK-induced IL-8 release was mimicked by the BK B2 receptor agonist (Tyr(Me)8)-BK and was potently inhibited by the selective B2 receptor antagonist HOE-140. These results suggest that human ASM can be a source of IL-8 and also that endogenous prostanoids, involving both COX-1 and COX-2, have a novel role in mediating BK-induced IL-8 production.

Adult↗
PubMed1998

Role of cyclo-oxygenase-2 induction in interleukin-1beta induced attenuation of cultured human airway smooth muscle cell cyclic AMP generation in response to isoprenaline.

Airway smooth muscle (ASM) in human asthma shows reduced relaxation and cyclic AMP generation in response to beta-adrenoceptor agonists. IL-beta attenuates cyclic AMP generation but the underlying mechanism is unclear. We have reported that IL-1beta induces cyclo-oxygenase-2 (COX-2) in human ASM cells and results in a marked increase in prostanoid generation with PGE2 and PGI2 as the major products. We investigated the role of COX-2 induction and prostanoid release (measured as PGE2) in IL-1beta induced attenuation of cyclic AMP generation in response to the beta-adrenoceptor agonist isoprenaline (ISO). Pre-treatment of human ASM cells with IL-1beta significantly attenuated cyclic AMP generation in response to high concentrations of ISO (1.0-10.0 microM) in a time- and concentration-dependent manner. The effect was accompanied by a high concentration of PGE2 release. The non-selective COX inhibitor indomethacin (Ind), the selective COX-2 inhibitor NS-398, the protein synthesis inhibitors cycloheximide (CHX) and actinomycin D and the steroid dexamethasone (Dex) all abolished the PGE2 release and prevented the attenuated cyclic AMP generation. COX substrate arachidonic acid time- and concentration-dependently mimicked IL-1beta induced attenuation and the effect was prevented by the non-selective COX inhibitors Ind and flurbiprofen, but not by NS-398, CHX and Dex. In contrast to IL-1beta, TNFalpha and IFNgamma, which are ineffective in inducing COX-2 and releasing PGE2 from human ASM cells, did not affect the cyclic AMP formation. Our study demonstrates that COX-2 induction and the consequent release of prostanoids plays a crucial role in IL-1beta induced attenuation of human ASM cell cyclic AMP response to ISO.

Adrenergic beta-Agonists↗