Risk of cancer in patients with ankylosing spondylitis: a nationwide cohort study in Taiwan.

Objective: To estimate the incidence of cancer among patients with ankylosing spondylitis (AS) and compare this risk with that of the general population.Method: We obtained data from Taiwan's National Health Insurance database on 19 289 patients with a first diagnosis of AS registered between 2000 and 2012 with no history of cancer before the diagnosis of AS. Standardized incidence ratios (SIRs) for all cancers and for site-specific cancers were used to assess whether AS was associated with an increased risk of cancer.Results: During the follow-up period, 485 patients developed cancer. The incidence rate was therefore 256.3 per 100 000 person-years. Compared with the general population, patients with AS had an increased risk of cancer [SIR 1.33, 95% confidence interval (CI) 1.20-1.47]. The SIR of cancer was higher in older patients; the risk increased from 8 years after initial diagnosis. Among solid tumours, the risk of melanoma was the highest (SIR 4.64, 95% CI 1.93-11.15), followed by prostate (SIR 2.53, 95% CI 2.01-3.19), thyroid (SIR 2.09, 95% CI 1.45-3.00), and bone cancer (SIR 2.00, 95% CI 1.01-3.99). Among haematological cancers, the risk of leukaemia was the highest (SIR 1.94, 95% CI 1.21-3.12). By contrast, the risks of oesophageal and oral cancers decreased in patients with AS.Conclusion: This nationwide population-based cohort study demonstrated that patients with AS in Taiwan are at an increased risk of cancer, particularly melanoma; prostate, thyroid, and bone cancers; and haematological malignancies.

Longitudinal associations of active renal disease with irreversible organ damage accrual in systemic lupus erythematosus.

OBJECTIVE: To examine longitudinal associations of active lupus nephritis with organ damage accrual in patients with systemic lupus erythematosus (SLE). METHODS: This study was performed using data from a large multinational prospective cohort. Active lupus nephritis at any visit was defined by the presence of urinary casts, proteinuria, haematuria or pyuria, as indicated by the cut-offs in the SLE Disease Activity Index (SLEDAI)-2K, collected at each visit. Organ damage accrual was defined as a change of SLICC-ACR Damage Index (SDI) score >0 units between baseline and final annual visits. Renal damage accrual was defined if there was new damage recorded in renal SDI domains (estimated glomerular filtration rate <50%/proteinuria >3.5 g per 24 h/end-stage kidney disease). Time-dependent hazard regression analyses were used to examine the associations between active lupus nephritis and damage accrual. RESULTS: Patients (N = 1735) were studied during 12,717 visits for a median (inter-quartile range) follow-up period of 795 (532, 1087) days. Forty per cent of patients had evidence of active lupus nephritis at least once during the study period, and active lupus nephritis was observed in 3030 (24%) visits. Forty-eight per cent of patients had organ damage at baseline and 14% accrued organ damage. Patients with active lupus nephritis were 52% more likely to accrue any organ damage compared with those without active lupus nephritis (adjusted hazard ratio = 1.52 (95% confidence interval (CI): 1.16, 1.97), p < 0.02). Active lupus nephritis was strongly associated with damage accrual in renal but not in non-renal organ domains (hazard ratios = 13.0 (95% CI: 6.58, 25.5) p < 0.001 and 0.96 (95% CI: 0.69, 1.32) p = 0.8, respectively). There was no effect of ethnicity on renal damage accrual, but Asian ethnicity was significantly associated with reduced non-renal damage accrual. CONCLUSION: Active lupus nephritis measured using the SLEDAI-2K domain cut-offs is associated with renal, but not non-renal, damage accrual in SLE.

Cancer risk among patients with systemic sclerosis: a nationwide population study in Taiwan.

OBJECTIVES: Systemic sclerosis (SSc) has been associated with high cancer risk. We compared the cancer risk among SSc patients with that among the general Taiwanese population. METHODS: The catastrophic illness registry of the Taiwan National Health Insurance Research Dataset (NHIRD) was used to identify patients diagnosed with SSc and cancer in Taiwan during 1996-2008. The standardized incidence ratio (SIR) for cancer was calculated, and mortality was ascertained using the data from the National Death Registry. RESULTS: Data analysis revealed that 2053 (472 men, 1581 women) Taiwanese individuals were diagnosed with SSc during the study period and 83 (30 men, 53 women) had cancer. The incidence of cancer was 6.9/1000 person-years. The most common cancer sites in male SSc patients were the lung (n = 10), oral cavity and pharynx (n = 8), and gastrointestinal tract (n = 4), and those in female patients were the breast (n = 11), lungs (n = 11), and blood (n = 6). Compared to the Taiwanese population of 1996, the all-cancer SIR for SSc was 1.63 [95% confidence interval (CI) 1.31-2.01]. Cancer risk was elevated for cancers of the lung (SIR 4.20), oral cavity and pharynx (SIR 3.67), and blood (SIR 3.50). A cancer diagnosis in SSc patients was associated with a hazard ratio (HR) of 2.15 (95% CI 1.30-3.53). Among cancer patients, a diagnosis of SSc was not associated with increased mortality. CONCLUSIONS: SSc patients are at high risk of developing cancer, especially of the lung, oral cavity and pharynx, and blood.

Incidence, cancer risk and mortality of dermatomyositis and polymyositis in Taiwan: a nationwide population study.

BACKGROUND: Nationwide data on the epidemiology of dermatomyositis (DM) and polymyositis (PM) were limited. OBJECTIVES: This study was to estimate the incidence, occurrence of cancer and mortality of DM and PM in Taiwan. METHODS: Both the register of critical illness of the Taiwan National Health Insurance Research Dataset and the National Death Registry of Taiwan were used to calculate estimates of the incidence, cancer association, and mortality of DM and PM between 2003 and 2007. RESULTS: A total of 803 DM and 500 PM cases were identified between 2003 and 2007. Mean age at diagnosis was 44·0 ± 18·3 years for DM and 49·2 ± 15·9 years for PM. The overall annual incidences of DM and PM were 7·1 (95% CI 6·6-7·6) and 4·4 (95% CI 4·0-4·8) cases per million population. The incidence of both DM and PM increased with age and reached a peak at age 50-59 years. One hundred and eleven (13·8%) patients with DM and 31 (6·2%) patients with PM had cancers. The diagnosis of most cancers was made after the diagnoses of DM (n = 71; 64·0%) and PM (n = 21; 67·7%). Overall, the standardized incidence ratios (SIR) for cancer were 5·36 (4·12-6·87) and 1·80 (1·10-2·79) among patients with DM and PM; however, during the first year, SIRs for cancer were 24·55 (95% CI 18·62-31·79) and 9·17 (95% CI 14·82-15·93) in patients with DM and PM, respectively. The most common types of cancer were nasopharyngeal cancer for men and breast cancer for women. Patients with DM and PM had standardized mortality ratios of 7·68 (6·41-9·01) and 5·29 (4·28-6·48). CONCLUSION: This study reports robust estimates of important aspects of the epidemiology of both DM and PM in Taiwan. This highlights the rarity of these diseases, and their associated cancer risks and increased mortality.

Hyperuricaemia and accelerated reduction in renal function.

OBJECTIVES: Hyperuricaemia has been linked to reduced renal function, and evidence indicates that it may be associated with acceleration of the decline in glomerular filtration rate (GFR) and progression of chronic kidney disease (CKD). METHODS: We analysed a population of subjects who had undergone serum uric acid (SUA) and serum creatinine measurements in a hospital-based cohort. Initial and final serum creatinine measurements were used to calculate the estimated glomerular filtration rate (eGFR) and the annual decline in eGFR. Cox regression was used to investigate the relationship between SUA and CKD progression. RESULTS: A total of 63,785 subjects were enrolled in the study during a 12-year follow-up period. The mean age at the time of initial serum creatinine measurement was 50.0 ± 14.9 years. Hyperuricaemic subjects had a significantly larger annual eGFR decline, both in absolute terms (2.5 ± 9.5 mL/min/1.73 m(2) per year) and as a percentage (2.8 ± 11.6% per year), as compared to the normouricaemia group (1.3 ± 9.6 mL/min/1.73 m(2) per year, 1.1 ± 11.1% per year, p < 0.001). After adjustment for age, sex, status of diabetes mellitus (DM) and hypertension, baseline eGFR, azotaemia, hypercholesterolaemia, and hyperglycaemia, hyperuricaemia was associated with a hazard ratio (HR) of 1.28 [95% confidence interval (CI) 1.23-1.33, p < 0.001] for an accelerated eGFR decline ≥ 3 mL/min/1.73 m(2) per year and an HR of 1.52 (95% CI 1.46-1.59) for CKD progression at the end of follow-up. CONCLUSION: Hyperuricaemia was associated with an accelerated decline in eGFR and higher risk of CKD progression. Therefore, renal function should be monitored closely in patients with hyperuricaemia.

Antinuclear antibody status and risk of death in children and adolescents.

OBJECTIVES: The association between the presence of antinuclear antibodies (ANA) and mortality has been rarely reported. The present study explored the value of ANA as a predictor of overall survival in children and adolescents. METHODS: Patients younger than 20 years who underwent ANA testing in Chang Gung Memorial Hospital (CGMH) from 2000 to 2008 were enrolled in this study. Mortality was ascertained by using the National Death Registry of Taiwan. Positive ANA titres were categorized as low (1:40 to 1:80), medium (1:160 to 1:320), and high (≥ 1:640). RESULTS: A total of 13 345 subjects (6579 males, 6766 females) were enrolled during the 9-year study period. The overall prevalence of low, medium, and high ANA titres was 20.8% (n = 2774), 6.0% (n = 804), and 2.5% (n = 338), respectively. During 45,140 person-years of follow-up, 146 deaths were identified and the crude mortality rates were 3.8 and 3.0 per 1000 person-years for subjects with positive and negative ANA test results, respectively (p = 0.130). Compared with ANA-negative subjects, the adjusted hazard ratio (HR) for all-cause mortality among those with a high ANA titre was 5.18 [95% confidence interval (CI) 3.13-8.57]. A low-to-medium ANA titre was not associated with increased mortality. Among the 18 deaths in individuals with a high ANA titre, 14 were due to systemic lupus erythematosus (SLE). In comparison, five out of 34 deaths among those with low-to-medium titres of ANA and none of those with negative ANA were related to SLE. CONCLUSIONS: Children and adolescents with high ANA titres should receive greater attention and monitoring to prevent unfavourable outcomes because they have a higher mortality risk than those with negative ANA results.

Epidemiology and mortality of systemic sclerosis: a nationwide population study in Taiwan.

OBJECTIVES: There have been few nationwide population studies of systemic sclerosis (SSc). We describe the epidemiological features of SSc in Taiwan. METHODS: The catastrophic illness registry of the Taiwan National Health Insurance Research Dataset (NHIRD) and the National Death Registry of Taiwan were used to calculate estimates of the incidence, prevalence, and mortality of SSc. RESULTS: A total of 1479 persons (325 males, 1154 females) with incident SSc were enrolled in the study. The annual incidence of SSc in Taiwan was found to be 10.9 cases (4.7 males, 17.4 females) per million population. During 2002-2007, the mean prevalence was 56.3 cases per million population. There were 204 deaths (70 males, 134 females) during the study period; 1-, 2-, and 5-year survival rates were 94.9, 92.0, and 83.2%, respectively. SSc patients had a standardized mortality ratio (SMR) of 3.24 [95% confidence interval (CI) 2.82-3.71] for all-cause mortality, as compared with the national population in 2002. There was excess mortality from neoplasms (SMR 1.50, 95% CI 1.03-2.11), cardiovascular diseases (2.23, 1.52-3.16), kidney disease (4.67, 2.66-7.64), gastrointestinal diseases (2.50, 1.27-4.46), and pulmonary diseases (3.20, 1.89-5.09). In addition to male sex and older age, cancer and end-stage renal disease (ESRD) diagnosis were risk factors for death, with hazard ratios (HRs) of 2.71 (95% CI 1.27-5.76) and 2.59 (1.14-5.90), respectively. CONCLUSION: SSc patients had a threefold greater risk of all-cause mortality than the general population of Taiwan. Male sex, older age, diagnosis of cancer, and ESRD were risk factors for death.

Gout and risk of non-alcoholic fatty liver disease.

OBJECTIVES: To investigate the association between gout and non-alcoholic fatty liver disease (NAFLD). METHODS: The study subjects were participants in a health-screening programme at Chang Gung Memorial Hospital from 2000 to 2006. Subjects were classified into eight groups based on serum urate (SU) level and gout status (≤ 4.9, 5.0-6.9, 7.0-8.9, and ≥ 9.0 mg/dL, without and with gout). The association between gout and NAFLD was assessed by multiple logistic regression. RESULTS: Among a total of 54 325 subjects, 1930 (3.6%) had gout and 6169 (11.3%) had NAFLD. The prevalence of NAFLD was significantly higher in subjects with gout (23.1%, n = 445) than in those without gout (10.9%, n = 5724, p < 0.001). Among subjects with NAFLD, the severity of NAFLD was higher in gout patients. Gout was associated with an increased risk for NAFLD [odds ratio (OR) 1.42, 95% confidence interval (CI) 1.25-1.60, p < 0.001], after adjustment for age, sex, presence of metabolic syndrome, and low estimated glomerular filtration rate (eGFR). With SU ≤ 4.9 mg/dL in the absence of gout as reference, the ORs (95% CI) for NAFLD, after adjustment for age, sex, presence of metabolic syndrome, and low eGFR, were, respectively, 2.16 (1.94-2.41), 3.98 (3.55-4.46), and 5.99 (5.19-6.90) for SU levels 2-4 in those without gout and 2.61 (1.39-4.91), 2.87 (2.04-4.04), 4.53 (3.70-5.56), and 6.31 (5.12-7.77) for SU levels 1-4 in those with gout. CONCLUSIONS: There was an independent association between gout and the risk for NAFLD. In addition, there was a dose-response relationship between SU and NAFLD in subjects with and without gout.

Synergic CSE1L/CAS, TNFR-1, and p53 apoptotic pathways in combined interferon-gamma/adriamycin-induced apoptosis of Hep G2 hepatoma cells.

Many cancers are chemotherapy-resistant. Chemotherapy combined with immunotherapy offers a potential avenue for the treatment of chemotherapy-resistant cancers. In this study, we investigated the apoptotic pathways induced by combined interferon-gamma/adriamycin treatment in Hep G2 cells. Our data showed that Hep G2 cells treated with combined interferon-gamma/adriamycin enhanced cell apoptosis in comparison with that of cells treated with adriamycin. Interferon-y increased TNFR-1, CSE1L/CAS (cellular apoptosis susceptibility protein), Bax, and Bad levels. Adriamycin increased p53 and Bax, but not TNFR- 1 and CAS levels. Interferon-y did not increase p53 accumulation; nevertheless it enhanced adriamycin-induced p53 accumulation. Overexpression of IRF-1 augmented the combined interferon-gamma/adriamycin-induced p53 accumulation. Interferon-gamma co-treatment increased the stability of p53 protein induced by adriamycin. Our data suggest that TNF-gamma may greatly enhance the combined interferon-gamma/chemotherapeutic drug-induced apoptosis of cancers. Our findings also indicate that CAS, TN-FR-1, p53, Bax, and Bad may be the targets for the interferon-y-based chemo-immunotherapy of the chemotherapy-resistant cancers.

Inhibitory effect of phorbol ester on bradykinin-induced phosphoinositide hydrolysis and calcium mobilization in cultured canine tracheal smooth muscle cells.

Regulation of the increase in inositol 1,4,5-trisphosphate (IP3) production and intracellular Ca2+ concentration ([Ca2+]i) by protein kinase C (PKC) was investigated in cultured canine tracheal smooth muscle cells (TSMCs). Stimulation of TSMCs by bradykinin (BK) led to IP3 formation and caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner. Pretreatment of TSMCs with phorbol 12-myristate 13-acetate (PMA, 1 microM) for 30 min blocked the BK-induced IP3 formation and Ca2+ mobilization. However, this inhibition was reduced after incubating the cells for 4 h with PMA. Inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate at 1 microM, did not inhibit these responses to BK. Prior treatment with staurosporine (1 microM), a PKC inhibitor, inhibited the effect of PMA on the BK-induced response, suggesting that the effect of PMA is mediated by the activation of PKC. In parallel experiments, a change of PKC activity was observed. PMA rapidly decreased PKC activity in the cytosol of TSMCs, while increasing it transiently in the cell membranes within 30 min. Thereafter the membrane-associated PKC activity decreased and persisted for at least 24 h of PMA treatment. Moreover, treatment with 1 microM PMA for 2 and 24 h did not significantly change the KD and Bmax of the BK receptor for [H]BK binding (control: KD = 2.3 +/- 0.3 nM, Bmax = 25.2 +/- 1.4 fmol/mg protein). These results suggest that activation of PKC inhibit IP3 accumulation and consequently attenuate [Ca2+]i increase or inhibit independently both responses. The PMA-induced inhibition of responses to BK was associated with an increase in membranous PKC activity.

Tumour necrosis factor-alpha enhances bradykinin-induced signal transduction via activation of Ras/Raf/MEK/MAPK in canine tracheal smooth muscle cells.

Inhalation of tumour necrosis factor-alpha (TNF-alpha) induced a bronchial hyperreactivity to contractile agonists. However, the mechanisms of TNF-alpha involved in the pathogenesis of bronchial hyperreactivity were not completely understood. Therefore, we investigated the effect of TNF-alpha on bradykinin (BK)-induced inositol phosphate (IP) accumulation and Ca(2+) mobilization, and up-regulation of BK receptor density in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with TNF-alpha potentiated BK-induced IP accumulation and Ca(2+) mobilization. However, there was no effect on the IP response induced by endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT), and carbachol. Pretreatment with PDGF B-chain homodimer (PDGF-BB) also enhanced BK-induced IP response. These enhancements induced by TNF-alpha and PDGF-BB might be due to an increase in BK B(2) receptor density (B(max)), since [3H]BK binding to TSMCs was inhibited by the B(2) selective agonist and antagonist, BK and Hoe 140, but not by the B(1) selective reagents. The enhancing effects of TNF-alpha and PDGF-BB were attenuated by PD98059 (an inhibitor of activation of MAPK kinase, MEK) and cycloheximide (an inhibitor of protein synthesis), suggesting that TNF-alpha may share a common signalling pathway with PDGF-BB via protein(s) synthesis in TSMCs. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed p42/p44 mitogen-activated protein kinase (MAPK) activation induced by TNF-alpha and PDGF-BB and attenuated the effect of TNF-alpha on BK-induced IP response, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by TNF-alpha might be, at least in part, mediated through activation of Ras/Raf/MEK/MAPK pathway in TSMCs.

Effect of forskolin on bradykinin-induced calcium mobilization in cultured canine tracheal smooth muscle cells.

The effects of increases in intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) on bradykinin (BK)-induced generation of inositol phosphates (IPs) and Ca2+ mobilization were investigated in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with either forskolin or dibutyryl cyclic AMP attenuated BK-stimulated responses. The inhibitory effects of these agents produced both a depression of the maximal response and a shift to the right of the concentration-response curves of BK. The water-soluble forskolin analogue L-858051, 7-deacetyl-7 beta-(r-N-methylpiperazino)-butyryl forskolin, significantly attenuated BK-stimulated IPs accumulation, while 1,9-dideoxy forskolin, an inactive forskolin, had little effect on IPs response. Moreover, SQ-22536, 9-(tetrahydro-2-furanyl)-9-H-purin-6-amine, an inhibitor of adenylate cyclase, and both H-89, N-(2-aminoethyl)-5-isoquinolinesulfonamide, and HA-1004, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide, inhibitors of cyclic AMP-dependent protein kinase (PKA), reversed the ability of forskolin to attenuate BK-stimulated IPs accumulation. The KD and Bmax, values of the BK receptor for [3H]BK binding were not significantly changed by forskolin treatment for 30 min and 4 h. The AlF4(-)-induced IPs accumulation was attenuated by forskolin, indicating that G protein(s) are directly activated by AlF4- and uncoupled to phospholipase C by forskolin treatment. These results suggest that activation of cyclic AMP/PKA might inhibit the BK-stimulated PI breakdown and consequently reduce the [Ca2+]i increases or inhibit independently both responses, which is distal to the BK receptor in canine cultured TSMCs.

Involvement of hypoxia-inducible factor-1-alpha in multidrug resistance induced by hypoxia in HepG2 cells.

Aim of the study was to explore the influence of hypoxia on multidrug resistance related genes and the potential role of hypoxia-inducible factor-1-alpha (HIF-1alpha) in formation of multidrug resistance in HepG2 human hepatocellular carcinoma cell line. HepG2 cells were subjected to hypoxia in a cohort of exposed time. A cell model stably expressing HIF-1alpha was established by liposome-mediated transfection of plasmid pcDNA3/HIF-1alpha into HepG2 cells. Apoptosis of HepG2 cells exposed to hypoxia or transfected by plasmid pcDNA3/HIF-1alpha was detected by Flow Cytometry after administration of chemotherapeutic drug (5-Fu). Real-time fluorescent quantitative PCR and Western-blot technique were used to analyze the expressions of multidrug resistance related genes mdr1, MRP1 and LRP at mRNA and protein level, respectively. Apoptosis Index of HepG2 cells exposed to hypoxia stepped down as exposed time extended after administration of 5-Fu. The expression of mdr1, MRP1 and LRP gene and protein revealed a hypoxic time-dependent induction and was synchronous with the alterations of HIF-1alpha in HepG2 cells exposed to hypoxia. The expressions of these multidrug resistance related genes were remarkably increased in HIF-1alpha transfected HepG2 cells as compared to empty vector transfected cells. Apoptosis index of HIF-1alpha transfected cells was obviously less than that of control cells when they were simultaneously exposed to 5-Fu for 24hrs. In conclusion, ambient hypoxia might be one of the causes for the formation of multidrug resistance in HepG2 human hepatocellular carcinoma cell line. Hypoxia-elicited multidrug resistance related protein expression might be a pathway for resistance of HepG2 cells to chemotherapeutics and HIF-1alpha might be involved in this process.

Sequencing and immunochemical characterization of the American cockroach per a 3 (Cr-PI) isoallergenic variants.

Two additional members of the American cockroach (Periplaneta americana) Per a 3 (Cr-PI) allergen, C13 and C28, were isolated and sequenced. They encoded proteins of 470 and 393 amino acids with two and no potential N-glycosylation sites, respectively. The molecular weights for C13 and C28 cloned proteins are 56,200 and 46,7000, with PI values of 7.06 and 6.54. C13 and C28 display 95.4% identity with several overlapping predicted central antigenic determinants. Both allergens were also found to have a 95% sequence homology with previously cloned C20 and share similar antigenic determinants, as defined by the structural prediction and ELISA analysis. However, the recombinant C13 and C28 allergens showed 26.3 and 94.7% skin reactivities on asthmatic patients while C20 elicited 47.4%. While no sequence similarity was found to other known allergens, these two aromatic amino acid-rich allergens were highly related to insect hemolymph proteins (28.7-36.5%), as with C20 cloned protein. Results suggest that these two are isoallergenic variants of C20. Sequence variations among isoforms, resulting a significant difference in skin reactivities, will be useful in elucidating the allergenic determinants.

Bradykinin-stimulated calcium mobilization in cultured canine tracheal smooth muscle cells.

Bradykinin (BDK)-induced increases in intracellular Ca2+ concentration ([Ca2+]i) were monitored in cultured canine tracheal smooth muscle cells (TSMCs) using a fluorescent Ca2+ indicator, Fura-2. BDK and kallidin caused an initial transient peak followed by a sustained elevation of [Ca2+]i in a concentration-dependent manner, with half-maximal stimulation (log EC50) obtained at -8.10 M and -8.04 M, respectively. The BDK-induced rise in [Ca2+]i was not affected by the BDK B1 receptor antagonist, des-Arg9[Leu8]-BDK (10 microM). However, the BDK B2 receptor antagonists des-Arg[Hyp3, Thi5,8, D-Phe7]-BDK and Hoe 140 had high affinity in antagonizing BDK with pKB values of 7.5 +/- 0.3 and 8.7 +/- 0.3, respectively. The sustained phase of the rise in [Ca2+]i was dependent on the presence of external Ca2+, as evidenced by a decline to the resting level on addition of EGTA. In the absence of external Ca2+, only an initial transient peak was seen which then declined to the resting level; a sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of BDK. Ca2+ influx was required for the changes in [Ca2+]i, since Ca(2+)-channel blockers, diltiazem, verapamil, and Ni2+, decreased both the initial and sustained elevation of [Ca2+]i in response to BDK. In conclusion, these findings indicate that the initial increase in [Ca2+]i stimulated by BDK acting on BDK B2 receptors is due to the release of Ca2+ from internal stores, followed by the influx of external Ca2+ into the cells. The influx of extracellular Ca2+ partially involves a diltiazem- and verapamil-sensitive Ca2+ channel.

Pharmacological characterization of bradykinin receptors in canine cultured tracheal smooth muscle cells.

1. [3H]-bradykinin was used to characterize the bradykinin receptors associated with canine cultured tracheal smooth muscle cells (TSMCs). Receptor binding assay showed that TSMCs had specific, saturable, high-affinity binding sites for [3H]-bradykinin. 2. The specific [3H]-bradykinin binding increased linearly with increasing cell concentrations. The equilibrium for association of [3H]-bradykinin with the bradykinin receptors was attained within 2 h at 4 degrees C and 1 h at room temperature, respectively. 3. Analysis of binding isotherms yielded an apparent equilibrium dissociation constant (KD) of 2.5 +/- 0.3 nM and a maximum receptor density (Bmax) of 25.1 +/- 0.3 fmol mg-1 protein. The Hill coefficient for [3H]-bradykinin binding was 1.00 +/- 0.02. The association (K1) and dissociation (K-1) rate constants were (8.67 +/- 2.60) x 10(6) M-1 min-1 and 0.024 +/- 0.005 min-1, respectively. KD, calculated from the ratio of K-1 and K1 was 2.8 +/- 0.5 nM, a value close to that of KD calculated from Scatchard plots of binding isotherms. 4. The B1 receptor selective agonist, (des-Arg9-bradykinin, 0.1 nM-10 microM) and antagonist ([Leu8, des-Arg9]-bradykinin, 0.1 nM-10 microM) did not did not inhibit the [3H]-bradykinin binding to TSMCs, which excludes the presence of B1 receptors in canine TSMCs. 5. The specific binding of [3H]-bradykinin to canine TSMCs was inhibited by B2 receptor selective antagonists ([D-Arg0, Hyp3, Thi5, D-Tic7, Oicl-bradykinin, Hoe 140, 0.1 nM-10 micro M and [D-Arg0, Hyp3,Thi5,8, D-Phe7-bradykinin, 0.1 nM-10 micro M) and agonists (bradykinin and kallidin, 0.1 nM-10 micro M) with a best fit by a one-binding site model. The order of potency for the inhibition of [3H]-bradykinin binding was kallidin = bradykinin = Hoe 140> [D-Arg0, Hyp3, Thi5,8, D-Phel-bradykinin.6. Preincubation of TSMCs with forskolin for 24 h led to an up-regulation of B2 receptors, increasing in Bmax from 25.1 +/- 0.3 to 218 +/- 24 fmol mg-1 protein without changing the KD values. [3H]-bradykinin binding to TSMCs was inhibited by the B2 receptor selective antagonists and agonists, but not by the B1 receptor selective reagents. The up-regulation of the B2 receptor by forskolin was mediated through protein synthesis, since cycloheximide blocked this response.7 It is concluded that the pharmacological characteristics of the bradykinin receptors in canine cultured TSMCs are primarily of the B2 receptor subtype.

The effect of cyclic AMP elevating agents on bradykinin- and carbachol-induced signal transduction in canine cultured tracheal smooth muscle cells.

1. The effects of cholera toxin (CTX), forskolin and dibutyryl cyclic AMP on bradykinin (BK)- and carbachol-induced accumulation of inositol phosphates (IPs) and Ca2+ mobilization were investigated in canine cultured tracheal smooth muscle cells (TSMCs). The BK-induced responses were mediated via a G protein which was not inhibited by CTX or pertussis toxin treatment. 2. BK-stimulated IPs accumulation and Ca2+ mobilization were potentiated by CTX (10 micrograms ml-1) pretreatment which was time-dependent. Maximal increase of these responses occurred after 24 h treatment with CTX. The concentration-effect relationship of BK-induced responses were shifted to the left and BK was substantially more effective in CTX-treated cells than in the control cells. This enhancing effect of CTX did not occur with carbachol. 3. Short-term (< 4 h) treatment with forskolin (10 microM) or dibutyryl cyclic AMP (1 mM) failed to accentuate BK-induced responses, but long-term (> 4 h) treatment of TSMCs with these agents mimicked the enhancing effect of CTX, suggesting that CTX-induced enhancement of BK responsiveness might be due to a rise in cyclic AMP. 4. Prolonged treatment of TSMCs with these agents was accompanied by an increase in cell surface [3H]-BK binding sites, which was inhibited by concurrent incubation with cycloheximide, an inhibitor of protein biosynthesis. Cycloheximide also abolished the potentiating actions of CTX, forskolin, and dibutyryl cyclic AMP on BK-induced IPs formation and Ca2+ mobilization. 5. The locus of this enhancement was further investigated by examining the effects of CTX, forskolin and dibutyryl cyclic AMP on A1F4(-)-induced IPs accumulation in canine TSMCs. AIF4-induced IPs accumulation was not affected by CTX, forskolin, or dibutyryl cyclic AMP treatment, supporting the contention that this stimulatory effect is located at the BK receptor level.6. These results demonstrate that the augmentation of BK-induced IPs accumulation and Ca2+mobilization produced by CTX, forskolin and dibutyryl cyclic AMP involves a cyclic AMP-dependent mechanism which is induced by a sustained increase in the level of intracellular cyclic AMP. CTX and forskolin may promote an increase of the synthesis of BK receptors, and thereby enhance BK-induced responses.

P2Y(2) receptor-mediated proliferation of C(6) glioma cells via activation of Ras/Raf/MEK/MAPK pathway.

1. Extracellular purine and pyrimidine nucleotides have been implicated in the regulation of several cellular functions including mitogenesis. In this study, experiments were conducted to characterize the P2Y receptor on C(6) glioma cells responsible for stimulating cell proliferation associated with mitogen-activated protein kinase (MAPK) activation. 2. UTP and ATP produced a similar effect on [(3)H]-thymidine incorporation in a time- and concentration-dependent manner, suggesting the involvement of P2Y(2) receptor in mediating proliferation of C(6) glioma cells. 3. In response to UTP, both p42 and p44 MAPK were activated in a time- and concentration-dependent manner using Western blot analysis with an anti-phospho-p42/p44 MAPK antibody. The phosphorylation reached maximal levels after 5 min and declining by 30 min. 4. Pretreatment with pertussis toxin (PTX) did not change these responses to UTP. Both DNA synthesis and phosphorylation of MAPK in response to UTP were attenuated by tyrosine kinase inhibitors, genistein and herbimycin A, protein kinase C (PKC) inhibitors, staurosporine and GF109203X, and removal of Ca(2+) by addition of BAPTA/AM plus EGTA. 5. UTP-induced [(3)H]-thymidine incorporation and p42/p44 MAPK phosphorylation was completely inhibited by PD98059 (an inhibitor of MEK1/2). Furthermore, we showed that overexpression of dominant negative mutants of Ras (RasN17) and Raf (Raf-301) completely suppressed MEK1/2 and p42/p44 MAPK activation induced by ATP and UTP. 6. These results conclude that the mitogenic effect of UTP mediated through a P2Y(2) receptor that involves the activation of Ras/Raf/MEK/MAPK pathway. UTP-mediated MAPK activation was modulated by Ca(2+), PKC, and tyrosine kinase associated with cell proliferation in cultured C(6) glioma cells.

Bradykinin-stimulated phosphoinositide metabolism in cultured canine tracheal smooth muscle cells.

1. Stimulation of bradykinin (BK) receptors coupled to phosphoinositide (PI) hydrolysis was investigated in canine cultured tracheal smooth muscle cells (TSMCs). BK, kallidin, and des-Arg9-BK, stimulated [3H]-inositol phosphates (IPs) accumulation in a dose-dependent manner with half-maximal responses (EC50) at 20 +/- 5, 13 +/- 4, and 2.3 +/- 0.7 nM, (n = 5), respectively. 2. D-Arg[Hyp3, D-Phe7]-BK and D-Arg[Hyp3, Thi5,8, D-Phe7]-BK, B2 receptor antagonists, were equipotent in blocking the BK-induced IPs accumulation with pKB = 7.1 and 7.3, respectively. 3. Short-term exposure of TSMCs to phorbol 12-myristate 13-acetate (PMA, 1 microM) attenuated BK-stimulated IPs accumulation. The concentrations of PMA that gave half-maximal and maximal inhibition of BK-induced IPs accumulation were 15 +/- 4 nM and 1 microM, n = 3, respectively. The inhibitory effect of PMA on BK-induced response was reversed by staurosporine, a protein kinase C (PKC) inhibitor, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC. 4. Prolonged incubation of TSMCs with PMA for 24 h, resulted in a recovery of receptor responsiveness which may be due to down-regulation of PKC. The inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate at 1 microM, did not inhibit this response. 5. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the G protein(s) can be directly activated by AlF4-, which is uncoupled from phospholipase C by PMA treatment. 6. Incubation of TSMCs in the absence of external Ca2+ or upon removal of Ca2+ by addition of EGTA, caused a decrease in IPs accumulation without changing the basal levels. Addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs stimulated IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) or BK. The combination of GTP gamma S and BK caused an additive effect on IPs accumulation.7. Pretreatment of TSMCs with cholera toxin enhanced BK-stimulated IPs accumulation, whereas there was no effect with pertussis toxin.8. These data suggest that BK-stimulated PI metabolism is mediated by the activation of BK B2 receptors coupling to a G protein which is not blocked by cholera toxin or pertussis toxin treatment and dependent on external Ca2+. The transduction mechanism of BK coupled to PI hydrolysis is sensitive to feedback regulation by PKC.