Effect of native and oxidized low-density lipoprotein on endothelial nitric oxide and superoxide production : key role of L-arginine availability.

BACKGROUND: Native and oxidized LDLs (n-LDL and ox-LDL) are involved in the atherogenic process and affect endothelium-dependent vascular tone through their interaction with nitric oxide (NO). METHODS AND RESULTS: In this study we evaluated directly, by using a porphyrinic microsensor, the effect of increasing lipoprotein concentrations on endothelial NO and superoxide (O(2)(-)) production. We investigated where lipoproteins may affect the L-arginine-NO pathway by pretreating cells with L-arginine, L-N-arginine methyl ester (L-NAME), and superoxide dismutase. Bovine aortic endothelial cells were exposed for 1 hour to increasing concentrations of n-LDL (from 0 to 240 mg cholesterol/dL) and ox-LDL (from 0 to 140 mg cholesterol/dL). A stimulated (calcium ionophore) NO concentration decreased to 29% of the control at n-LDL concentration of 80 mg cholesterol/dL and to 15% of the control at 20 mg cholesterol/dL of ox-LDL. L-Arginine partially neutralized the inhibitory effect of n-LDL and ox-LDL on the NO generation. Superoxide dismutase pretreatment did not modify NO production, whereas L-NAME blunted NO generation at all LDL concentrations. O(2)(-) production was increased at low n-LDL and very low ox-LDL concentrations; this was reversed by L-arginine. CONCLUSIONS: These findings confirm the inhibitory role of n-LDL and ox-LDL on NO generation and suggest that lipoproteins may induce a decreased uptake of L-arginine. The local depletion of the L-arginine substrate may derange the NO synthase, leading to overproduction of O(2)(-) from oxygen, the other substrate of NO synthase.

Benzodiazepines with different half-life and falling in a hospitalized population: The GIFA study. Gruppo Italiano di Farmacovigilanza nell'Anziano.

In recent years, the use of benzodiazepines has been recognized as an independent risk factor for falls among the elderly. To evaluate the role of different types of benzodiazepines in determining falls in a hospitalized geriatric population, we conducted a prospective study among 7908 patients consecutively admitted in 58 clinical centers of the Gruppo Italiano di Farmacovigilanza nell'Anziano (GIFA), during an 8-month observation period (1991 and 1993). Over 70% of the patients were older than 65 years, 50% were women, and 23. 6% had a benzodiazepine prescription during hospital stay. The number of patients who experienced one or more falls during follow-up was 174 (2.2%). Sixty falls occurred among patients taking benzodiazepines (3.2%) and 114 (1.9%) among those who did not use benzodiazepines; the crude odds ratio for users versus non-users was 1.7 (95% CI 1.2-2.3). Multivariate logistic regression analysis showed that benzodiazepines with very short (OR 1.9; CI 1.03-3.3) and short half-life (OR 1.8; CI 1.2-2.8) were positively associated with falls during hospital stay. Patients who used other psychotropic agents (OR 2.3; CI 1.7-3.4), antidiabetic agents (OR 1. 5; CI 1.03-2.2), patients with presence of cognitive impairment (OR 1.6; CI 1.08-2.3), high level of comorbidity (OR 1.7; CI 1.05-2.9), more advanced age (>80 years, OR 2.7; CI 1.5-4.7) and those who stayed in the hospital for 17 days or more (OR 2.1; CI 1.4-3.3) were also at a greater risk. These findings suggest that benzodiazepines with short and very short half-life are an important and independent risk factor for falls and their prescription to elderly hospitalized patients should be carefully evaluated.

Detection of nitric oxide release induced by bradykinin in guinea pig trachea and main bronchi using a porphyrinic microsensor.

Indirect evidence using nitric oxide (NO) synthase (NOS) inhibitors suggests that in guinea-pig airways bradykinin releases bronchoprotective NO. In this study, using a recently developed electrochemical method of NO measurement based on a porphyrinic microsensor, we investigated whether bradykinin releases NO from guinea-pig airways and whether the epithelium is the main source of NO. Further, the Ca(2+)-dependence of bradykinin-induced NO release was assessed stimulating airway preparations with bradykinin in Ca(2+)-free conditions. We also studied the immunohistochemical distribution of the Ca(2+)- dependent constitutive isoforms of NOS (constitutive NOS [cNOS]: neuronal and endothelial [ecNOS]) in our preparations. The porphyrinic microsensor was placed in the bathing fluid onto the mucosal surface of tracheal or main bronchial segments. Addition of bradykinin vehicle (0.9% saline) did not cause any detectable change of the baseline signal. Addition of bradykinin caused an upward shift of the baseline that reached a maximum within 1 to 2 s. The amplitude of the response to bradykinin was concentration-dependent between the range 1 nM to 10 microM, with a maximum effect at 10 microM. Bradykinin-induced NO release was higher in tracheal than in main bronchial segments. The selective bradykinin B(2) receptor antagonist D-Arg(0)-[Hyp(3), Thi(5), D-Tic(7), Oic(8)]bradykinin (1 microM) inhibited NO release induced by a submaximum concentration of bradykinin (1 microM). The ability of bradykinin to release NO was markedly reduced in epithelium-denuded segments, and abolished in Ca(2+)-free conditions and after pretreatment with N(G)-monomethyl-L-arginine (100 microM), but not with N(G)-monomethyl-D-arginine. Both cNOS isoforms were present in trachea and main bronchi, ecNOS being the predominant isoform in the epithelium. The study shows that bradykinin via B(2) receptor activation caused a rapid and Ca(2+)-dependent release of NO, mainly, but not exclusively, derived from the epithelium. It also shows that both cNOS isoforms may be involved in bradykinin-evoked NO release.

Characterization of the endothelin receptor subtype mediating epithelium-derived relaxant nitric oxide release from guinea-pig trachea.

1. The endothelin (ET) receptor subtype that mediates niric oxide (NO)-dependent airway relaxation in tracheal tube preparations precontracted with carbachol and pretreated with indomethacin was investigated. The release of NO induced by ET from guinea-pig trachea using a recently developed porphyrinic microsensor was also measured. 2. ET-1 (1 pM-100 nM) contracted tracheal tube preparations pretreated with the NO-synthase inhibitor, L-NMMA, and relaxed, in an epithelium-dependent manner, preparations pretreated with the inactive enantiomer D-NMMA. The effect of L-NMMA was reversed by L-Arg, but not by D-Arg. 3. The selective ET(B) receptor agonists, IRL 1620 or sarafotoxin S6c, both (1 pM-100 nM) contracted tracheal tube preparations in a similar manner either after treatment with D-NMMA or with L-NMMA. In the presence of the ET(A) receptor antagonist, FR139317 (10 microM), ET-1 administration resulted in a contraction that was similar after either L-NMMA or D-NMMA. In the presence of the ET(B) receptor antagonist, BQ788 (1 microM), ET-1 relaxed and contracted tracheas pretreated with D-NMMA and L-NMMA, respectively. 4. Exposure of tracheal segments to ET-1 (1-1000 nM) caused a concentration-dependent increase in NO release that was reduced by L-NMMA. IRL1620 (1 microM) did not cause any significant NO release. FR139317 (10 microM), but not, BQ788 (1 microM), inhibited the NO release induced by ET-1. 5. These results demonstrate that in the isolated guinea-pig trachea activation of ET(B) receptors results in a contractile response, whereas activation of ET(A) receptors cause both a contraction, and an epithelium-dependent relaxation that is mediated by NO release.

Fibrinolytic and coagulation factors in very old subjects: association with lipoprotein profile and anthropometric variables.

BACKGROUND: We evaluated plasminogen activator inhibitor-1 (PAI-1), factor VII activity (FVII), and fibrinogen in a sample of octo-nonagenarians. Furthermore, we investigated the relationship of these fibrinolytic and coagulation parameters with lipoprotein profile and anthropometric variables in the absence or presence of disability. METHODS: We enrolled a population of 162 octo-nonagenarians, divided in two groups on the basis of presence or absence of disability in the activity of daily living (ADL). All the anthropometric determinations were carried out according to standardized methods. Blood samples for hemostatic and lipid determinations were collected after overnight fasting and resting. RESULTS: PAI-1 activity and fibrinogen levels were significantly higher in disabled (DIS) compared to free-living (FL) adults, whereas FVII did not show differences in the two groups. PAI-1 activity and FVII positively correlated to anthropometric parameters (body mass index, subscapular and tricipital skinfold thickness) in both DIS and FL. No correlations were found between fibrinogen and other variables in FL, whereas a negative relation with high density lipoprotein-cholesterol levels emerged in DIS. FVII was positively related with total cholesterol low density lipoprotein-cholesterol, and apolipoprotein B in both FL and DIS. CONCLUSIONS: In a sample of octo-nonagenarians, PAI-1 activity and FVII show a significant correlation with several anthropometric and lipoprotein parameters, suggesting that these variables are strongly associated with body composition and lipid metabolism independent from age and disability. DIS presented higher PAI-1 and fibrinogen levels; this observation may take in account the high prevalence of vascular diseases and also occult inflammation, which are known to affect these parameters.