Tempol-nebivolol therapy potentiates hypotensive effect increasing NO bioavailability and signaling pathway

Nebivolol is a third generation beta blocker with endothelial nitric oxide synthase (eNOS) agonist properties. Considering the role of reactive oxygen species (ROS) in the uncoupling of eNOS, we hypothesized that the preadministration of an antioxidant as tempol, could improve the hypotensive response of nebivolol in normotensive animals increasing the nitric oxide (NO) bioavailability by a reduction of superoxide (O2(•-)) basal level production in the vascular tissue. Male Sprague Dawley rats were given tap water to drink (control group) or tempol (an antioxidant scavenger of superoxide) for 1 week. After 1 week, Nebivolol, at a dose of 3 mg/kg, was injected intravenously to the control group or to the tempol-treated group. Mean arterial pressure, heart rate, and blood pressure variability were evaluated in the control, tempol, nebivolol, and tempol nebivolol groups, as well as, the effect of different inhibitor as Nβ-nitro-l-arginine methyl ester (L-NAME, a Nitric oxide synthase blocker) or glybenclamide, a KATP channel inhibitor. Also, the expression of α,β soluble guanylate cyclase (sGC), phospho-eNOS, and phospho-vasodilator-stimulated phosphoprotein (P-VASP) were evaluated by Western Blot and cyclic guanosine monophosphate (cGMP) levels by an enzyme-linked immunosorbent assay (ELISA) commercial kit assay. We showed that pretreatment with tempol in normotensive rats produces a hypotensive response after nebivolol administration through an increase in the NO bioavailability and sGC, improving the NO/cGMP/protein kinase G (PKG) pathway compared to that of the nebivolol group. We demonstrated that tempol preadministration beneficiates the response of a third-generation beta blocker with eNOS stimulation properties, decreasing the basal uncoupling of eNOS, and improving NO bioavailability. Our results clearly open a possible new strategy therapeutic for treating hypertension.

Evaluation of indigenous bacterial strains for biocontrol of the frogeye leaf spot of soya bean caused by Cercospora sojina

AIMS

Assessment of biological control of Cercospora sojina, causal agent of frogeye leaf spot (FLS) of soya bean, using three indigenous bacterial strains, BNM297 (Pseudomonas fluorescens), BNM340 and BNM122 (Bacillus amyloliquefaciens).

METHODS AND RESULTS

From cultures of each bacterial strain, cell suspensions and cell-free supernatants were obtained and assayed to determine their antifungal activity against C. sojina. Both mycelial growth and spore germination in vitro were more strongly inhibited by bacterial cell suspensions than by cell-free supernatants. The Bacillus strains BNM122 and BNM340 inhibited the fungal growth to a similar degree (I ≈ 52-53%), while cells from P. fluorescens BNM297 caused a lesser reduction (I ≈ 32-34%) in the fungus colony diameter. The foliar application of the two Bacillus strains on soya bean seedlings, under greenhouse conditions, significantly reduced the disease severity with respect to control soya bean seedlings and those sprayed with BNM297. This last bacterial strain was not effective in controlling FLS in vivo.

CONCLUSIONS

Our data demonstrate that the application of antagonistic bacteria may be a promising and environmentally friendly alternative to control the FLS of soya bean.

SIGNIFICANCE AND IMPACT OF THE STUDY

  To our knowledge, this is the first report of biological control of C. sojina by using native Bacillus strains.

Signal transduction pathways and haem oxygenase induction in soybean leaves subjected to salt stress

We have previously demonstrated that the induction of haem oxygenase-1 (EC 1.14.99.3) plays a protective role for soybean plants against cadmium and UV-B stress. Here, we have investigated the possible signal transduction pathways involved in haem oxygenase-1 induction in leaves of soybean plants subjected to salt stress. Treatment with 100 mM NaCl during 48 h increased thiobarbituric acid reactive substances by 30%, whereas GSH decreased by 50%, with respect to controls. These effects were prevented by pre-incubation with diphenyleneiodonium (DPI; an NADPH oxidase inhibitor), [1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ; a guanylate cyclase inhibitor) or LaCl3 (calcium channel blocker). NaCl at 100 mM produced in situ accumulation of H2O2 and O2*-, which were also prevented by DPI, ODQ or LaCl3. Moreover, salt-induced haem oxygenase-1 activity was also totally abolished by pretreatment with the different inhibitors. These results clearly demonstrated that the signal transduction pathways involved in oxidative stress triggered by salt stress were similar to those implicated in haem oxygenase-1 induction, and provide additional information suggesting that haem oxygenase might play a key role in the antioxidative protection machinery of higher plants.