Low molecular mass dinitrosyl nonheme-iron complexes up-regulate noradrenaline release in the rat tail artery

Carbon monoxide dehydrogenase in mycobacteria possesses a nitric oxide dehydrogenase activity

CO dehydrogenase (CO-DH) catalyzes the oxidation of CO to CO(2) in carboxydobacteria. Cell-free extracts prepared from several mycobacteria, including Mycobacterium tuberculosis H37Ra, showed NO dehydrogenase (NO-DH) activity in a reaction mixture containing sodium nitroprusside (SNP) as the source of NO. The association of the NO-DH activity with CO-DH was revealed by activity staining and confirmed by enzyme assay with purified CO-DH from Mycobacterium sp. strain JC1, a carboxydotrophic mycobacterium. SNP stimulated the production of CO-DH with a coincidental increase in NO-DH activity in the bacterium, further supporting this association and implying the existence of a possible SNP-induced CO-DH gene expression. The addition of purified CO-DH to cultures of Escherichia coli revealed that the enzyme protected E. coli from SNP-induced killing in a dose-dependant way. The present results indicate that mycobacterial CO-DH also acts as a NO-DH, which may function in the protection of mycobacterial pathogens from nitrosative stress during infection.

Iron nitrosyl complexes as models for biological nitric oxide transfer reagents

Owing to the indiscriminate reactivity of the free NO radical, intricate control mechanisms are required for storage, transport and transfer of NO to its various biological targets. Among the proposed storage components are protein-bound thionitrosyls (Rprotein-SNO) and protein-bound dinitrosyl iron complexes. Current knowledge suggests the latter are derived from iron-sulfur cluster degradation in the presence of excess NO. Mobilization of protein-bound NO could involve NO or Fe(NO)2 unit transfer to small serum molecules such as glutathione, free cysteine, or iron-porphyrins. The study reported is of a reaction model which addresses the key steps in NO transfer from a prototypal iron dinitrosyl complex. While the N,N'-bis(2-mercaptoethyl)-N,N'-diazacyclooctane (bme-daco) ligand typically binds in square-planar N2S2 coordination, it also serves as a bidentate dithiolate donor for tetrahedral structures in the preparation of the (H+bme-daco)Fe(NO)2 derivative (Chiang et al., J. Am. Chem. Soc. 126:10867-10874, 2004). The removal of one NO produces the mononitrosyl complex, (bme-daco)Fe(NO), and simplifies studies of NO release mechanisms. We have used heme-type model complexes, Fe or Co porphyrins as NO acceptors, yielding (porphyrin)M(NO), where M is Fe or Co, and monitored reactions by nu(NO) Fourier transform IR spectroscopy. Reaction products were verified by electrospray ionization mass spectrometry. Rudimentary mechanistic studies suggest a role for HNO in the NO release from the dinitrosyl; the mononitrosyl benefits as well from acid catalysis. Other NO uptake complexes such as [(N2S2)Fe]2 [N2S2 is bme-daco or N,N'-bis(2-mercapto-2-methylpropyl)-daco] are shown to form Fe(NO) mononitrosyls with stability and spectroscopic signatures similar to those of the porphyrins.

Effects of a controlled pedometer-intervention trial for low-active adolescent girls

PURPOSE

This intervention compares the effectiveness of daily step count targets with time-based prescription for increasing the health-related physical activity of low-active adolescent girls.

METHODS

We assigned participants (N = 85, mean age 15.8 +/- 0.8 yr) depending on school attended to a control (CON), pedometer (PED), or minutes (MIN) group. The intervention groups were involved in a 12-wk physical activity self-monitoring and educative program. The only difference between the intervention groups was that the PED group set daily step count targets whereas the MIN group set daily time-based goals for physical activity involvement. Pre-, mid-, and postintervention changes in physical activity (4-d blinded step count and 3-d physical activity recall) and body mass index (BMI) were assessed using a series of 3 (group assignment) x 3 (time) ANOVA. Where significant interactions were found, separate follow-up simple main effects tests were used.

RESULTS

At postintervention, only the PED group had significantly increased their total activity as measured by a 4-d step count, when compared with the control (P = 0.03, ES = 0.13). The group, time, and interaction effects for 4-d step count were significant, indicating that although both the participants in the PED and the MIN groups significantly increased their step count across the 12-wk intervention (P = 0.00-0.01), the participants in the PED group had a greater increase at the midintervention time point (P = 0.04, ES = 0.10). No pre-, mid-, or postintervention changes were reported in any group for BMI (F = 1.18, P = 0.32).

CONCLUSION

The use of pedometers and daily step count targets with low-active adolescent girls may result in short-term (6 wk) enhanced physical activity related outcomes when compared with traditional time-based physical activity prescriptions. However, both interventions appear to result in similar improvements in physical activity when duration of the observation is extended to 12 wk.

Bismercaptoethanediazacyclooctane as a N2S2 Chelating Agent and Cys−X−Cys Mimic for Fe(NO) and Fe(NO)2

The N-protonated bismercaptoethanediazacyclooctane serves as a bidentate dithiolate ligand to oxidized Fe(NO)(2) of Enemark-Feltam notation, E-F [Fe(NO)(2)],(9) mimicking Cys-X-Cys binding of Fe(NO)(2) to proteins or thio-biomolecules. The neutral compound is characterized by the well-known g = 2.03 EPR signal which is a hallmark of dinitrosyl iron complexes, DNIC's. The Fe(NO)(2) unit can be removed from the chelate by excess PhS(-), producing (PhS)(2)Fe(NO)(2)(-). Transfer of NO from Fe(H(+)bme-daco)(NO)(2) (nu(NO) = 1740, 1696 cm(-)(1)) to Fe(II) of [(bme-daco)Fe](2) yields the five-coordinate, square-pyramidal N(2)S(2)Fe(NO) (nu(NO) = 1649 cm(-)(1)), where NO is in the apical position. Its isotropic EPR signal at g = 2.05 is consistent with E-F [Fe(NO)](7) formulation. In excess NO, Roussin's red ester-type molecules are formed as dinuclear or tetranuclear species, [(micro-SRS)[Fe(2)(NO)(4)]](n)() (n =1, 2). These well-characterized molecules furnish reference points for positions and patterns in nu(NO) vibrational spectroscopy expected to be useful for in vivo studies of NO degradation of iron-sulfur clusters in ferredoxins.

Inhibition of arterial contraction by dinitrosyl-iron complexes: critical role of the thiol ligand in determining rate of nitric oxide (NO) release and formation of releasable NO stores by S-nitrosation

The inhibition of arterial tone produced by two nitric oxide (NO) derivatives of biological relevance, dinitrosyl-iron complexes with cysteine (DNIC-CYS) or with glutathione (DNIC-GSH), was compared. Both compounds induced vasorelaxation within the same concentration range (3-300 nM) in endothelium-denuded rat aortic rings. Consistent with a faster rate of NO release from DNIC-CYS than from DNIC-GSH, the relaxant effect of DNIC-CYS was rapid in onset and tended to recover with time, whereas the one of DNIC-GSH developed slowly and was sustained. In addition, DNIC-GSH (0.3 and 1 microM) but not DNIC-CYS (1 microM) induced, even after washout of the drug, a persistent hyporesponsiveness to vasoconstrictors and a relaxant effect of low molecular weight thiols like N-acetylcysteine (NAC, which can displace NO from preformed NO stores). Both effects of DNIC-GSH were associated with elevation of cyclic GMP content and were attenuated by NO scavengers or a cyclic GMP-dependent protein kinases inhibitor. In rings previously exposed to DNIC-GSH, addition of mercuric chloride (which can cleave the cysteine-NO bond of S-nitrosothiols) elicited relaxation, completely blunted the one of NAC and also abolished the persistent elevation of NO content. In conclusion, this study shows that whereas both DNIC-CYS and DNIC-GSH elicited a NO release-associated relaxant effect in isolated arteries, only DNIC-GSH induced an inhibition of contraction which persisted after drug removal. The persistent effect of DNIC-GSH was attributed to the formation of releasable NO stores in arterial tissue, most probably as S-nitrosothiols. Thus, the nature of the thiol ligand plays a critical role in determining the mechanisms and duration of the effect of LMW-DNIC in arteries.