Publications by authors named "Sergio Franchi-Micheli"

5 Publications

  • Page 1 of 1

Losartan counteracts the hyper-reactivity to angiotensin II and ROCK1 over-activation in aortas isolated from streptozotocin-injected diabetic rats.

Cardiovasc Diabetol 2009 Jun 22;8:32. Epub 2009 Jun 22.

Dept. of Pharmacology, University of Florence, Viale G, Pieraccini 6, Florence, Italy.

Background: In streptozotocin-injected rats (STZ-rats), we previously demonstrated a role for angiotensin II (AT-II) in cardiac remodelling and insulin resistance partially counteracted by in vivo treatment with losartan, an AT-II receptor antagonist.We now aimed to investigate the effect of treating diabetic STZ-rats with losartan on diabetes vascular response to vasoconstrictors.

Methods: Male Wistar rats were randomly divided in four groups, two of them were assigned to receive losartan in the drinking water (20 mg/kg/day) until the experiment ending (3 weeks afterward). After 1 week, two groups, one of which receiving losartan, were injected in the tail vein with citrate buffer (normoglycemic, N and normoglycemic, losartan-treated, NL). The remaining received a single injection of streptozotocin (50 mg/kg in citrate i.v.) thus becoming diabetic (D) and diabetic losartan-treated (DL). Plasma glycaemia and blood pressure were measured in all animals before the sacrifice (15 days after diabetes induction).In aortic strips isolated from N, NL, D and DL rats we evaluated i) the isometric concentration-dependent contractile response to phenylephrine (Phe) and to AT-II; ii) the RhoA-kinase (ROCK1) activity and expression by enzyme-immunoassay and Western blot respectively.

Key Results: The concentration-dependent contractile effect of Phe was similar in aortas from all groups, whereas at all concentrations tested, AT-II contraction efficacy was 2 and half and 1 and half times higher in D and DL respectively in comparison with N and NL. AT-II contracture was similarly reduced in all groups by AT-II receptor antagonists, irbesartan or irbesartan plus PD123319. HA-1077 (10 microM), an inhibitor of ROCK1 activity, reduced AT-II efficacy (Deltamg/mg tissue w.w.) by -3.5 +/- 1.0, -4.6 +/- 1.9, -22.1 +/- 2.2 and -11.4 +/- 1.3 in N, NL, D and DL respectively). ROCK1 activity and expression were higher in D than in N/NL and DL aortas.

Conclusion And Implications: Aortas isolated from STZ-rats present hyper-contracture to AT-II mainly dependent on the up-regulation of ROCK1 expression/activity. In vivo losartan treatment partially corrects AT-II hyper-contracture, limiting the increase in ROCK1 expression/activity. These data offer a new molecular mechanism supporting the rationale for using losartan in the prevention of diabetic vascular complications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1475-2840-8-32DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711933PMC
June 2009

Influence of resting tension on protease-activated receptor-mediated relaxation in guinea-pig tracheas.

Pulm Pharmacol Ther 2005 30;18(2):141-50. Epub 2004 Dec 30.

Department of Pharmacology, University of Florence, Viale Pieraccini, 6, 50139 Firenze, Italy.

We investigate the role of resting tension on thrombin (THR) induced relaxation of guinea-pig tracheas precontracted with acetylcholine (ACh). Isometric contractions of isolated guinea-pig tracheas were recorded at 4 and 6 g resting tension; and ACh dose-response curves were performed. THR relaxed ACh-precontracted tracheas and this effect was mimicked by the type 2 protease activating receptor agonist peptide (PAR-2 AP) and trypsin. The relaxant effect of 3 U ml(-1) THR and 100 nmol ml(-1) PAR-2 AP was prevented at 4 g by preincubation with the nitric oxide synthase (NOS) inhibitor l-NAME and at 6g resting tension by ibuprofen and diclofenac. However, adenosine trisphospahate (ATP) relaxation was totally prevented by cyclooxygenase (COX) inhibitors but not by NOS inhibitors at both resting tensions. Resting tension influenced the effect of PGE2 on contractile tone of isolated guinea-pig tracheas, the maximal relaxation being -11.1+/-2.97 and -2.0+/-0.4 6 mg mg(-1) tissue wet weight at 6 and 4 g, respectively. Moreover, 30 nmol ml(-1) PGE2 can relax ACh-precontracted tracheas, being the effect up to 91 and 30% at 6 and 4 g, respectively. These data demonstrate that trachea responsiveness is highly dependent on the smooth muscle length, revealing new aspects of stretch-activated receptors that can influence trachea responsiveness in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pupt.2004.11.006DOI Listing
May 2005

Pirenoxine prevents oxidative effects of argon fluoride excimer laser irradiation in rabbit corneas: biochemical, histological and cytofluorimetric evaluations.

J Photochem Photobiol B 2005 Jan;78(1):35-42

Department of Preclinical and Clinical Pharmacology, University of Florence, V.le Pierraccini, 6, Florence, Italy.

The production of reactive oxygen species (ROS) associated with excimer laser irradiation is recognized as a possible cause of corneal haze following photorefractive keratectomy (PRK). Our work was aimed at investigating in vitro the oxidative effects induced by subablative laser fluences and at demonstrating the protective effectiveness of pirenoxine. Comparative trials of subablative fluence on rabbit eyes with or without 10(-5) M pirenoxine were carried out. Superoxide anion (O(2)(-)), conjugated diene (CD), and thiobarbituric acid reagent substance (TBARS) formation were analyzed. Cellular death was evaluated by flow cytometry. Histological examinations were also performed. No appraisable differences in O(2)(-),CD,andTBARS formation were detected soon after irradiation, whereas they all increased following incubation. Pirenoxine inhibited such increases. Cytofluorimetric and histological observations gave coherent results. The experimental data indicate that oxidative and toxic effects are ascribable to ROS avalanches triggered by laser irradiation-induced photodissociation and are inhibited by pirenoxine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jphotobiol.2004.09.005DOI Listing
January 2005

Antioxidant protection in cultured corneal cells and whole corneas submitted to UV-B exposure.

J Photochem Photobiol B 2003 Oct;71(1-3):59-68

Department of Preclinical and Clinical Pharmacology, University of Florence, V.le Pieraccini 6, Florence 50139, Italy.

Several corneal pathologies are characterized by the presence of reactive oxygen species (ROS); therefore, we evaluated the protection afforded by pirenoxine and melatonin to corneal cell culture and whole rabbit cornea from ultraviolet exposure and other oxidant systems. Rabbit cornea cell (SIRC) plates and whole corneas were exposed to UV-B (80 or 800 mJ/cm2) or incubated with fMLP-stimulated autologous macrophages, in the presence or absence of pirenoxine or melatonin (10(-5) M). The protective activity of compounds was assessed by measuring superoxide anion formation, inhibition of oxidation and mitochondrial viability. Moreover the ex vivo protective effect of pirenoxine and melatonin was verified in the whole cornea submitted to UV-B exposure in vitro. Our experimental data demonstrate that pirenoxine and melatonin were able to inhibit the superoxide formation and oxidative effect in cell culture and whole rabbit corneas submitted to UV-B exposure or to incubation with fMLP-stimulated autologous macrophages. Mitochondrial viability was restored in epithelial cells of rabbit cornea but not in SIRCs. Moreover, both compounds are also able to increase ex vivo epithelial corneal cell defences against the in vitro UV-B induced lipid peroxidation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jphotobiol.2003.07.004DOI Listing
October 2003

The ACh-induced contraction in rat aortas is mediated by the Cys Lt1 receptor via intracellular calcium mobilization in smooth muscle cells.

Br J Pharmacol 2003 Feb;138(4):707-15

Department of Pharmacology, University of Florence, Viale Pieraccini, 6 50139 Florence, Italy.

1. Our previously published data indicate that an endogenously produced 5-lipoxygenase metabolite can strongly contract isolated endothelium-preserved rat aortic strips when cyclo-oxygenase isoenzymes are inhibited. Therefore, we decided to investigate if cysteinyl-containing leukotrienes (Cys Lts) are involved in this endothelium-dependent contraction. 2. The isometric contraction of endothelium-preserved rat aortic strips was recorded in preparations preincubated with 5 microM indomethacin and precontracted with phenylephrine, adjusting resting tension at 0.7 g. Acetylcholine (ACh) contracted control strips. Montelukast and MK-571, selective type 1 Cys Lts receptor (Cys Lt(1)) antagonists and the Cys Lt(1)/Cys Lt(2) (type 2 Cys Lts receptor) antagonist BAYu9773 dose-dependently prevented ACh-induced contraction, their IC(50)s being 2.2, 3.1 and 7.9 nM respectively. The leukotriene B4 receptor antagonist U75302 was far less potent (IC(50) 1.5 microM). 3. In rat aorta smooth muscle cells (RASMs), Western blot analysis showed the presence of Cys Lt(1) and Cys Lt(2) receptors, the Cys Lt(1) receptor being predominantly expressed. 4. In fura-2 loaded RASMs, LTD4 (0.01-100 nM) and LTC4 (200-800 nM) dose-dependently increased intracellular calcium concentration ([Ca(2+)](i)). Montelukast (1-100 nM) reduced LTD4-induced [Ca(2+)](i) increase, its IC(50) being approximately 10 nM. BAY u9773 exhibited significantly low effectiveness. 5. LTD4 (10 nM) induced a redistribution of smooth muscle actin fibres throughout the cytoplasm as visualized by confocal microscopy. 6. In conclusion, Cys Lt(1) activation by endogenously produced Cys Lts, can contract rat aortas, while Cys Lt(2) only marginally influences aortic tone. Intracellularly, this effect is mediated by an increase in [Ca(2+)](i). Therefore, Cys Lts, by inducing vascular contraction, can contribute to systemic hypertension.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/sj.bjp.0705087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1573698PMC
February 2003