Downregulation of carbon monoxide as well as nitric oxide contributes to peripheral chemoreflex hypersensitivity in heart failure rabbits.

Peripheral chemoreflex sensitivity is potentiated in clinical and experimental chronic heart failure (CHF). Downregulation of nitric oxide (NO) synthase (NOS) in the carotid body (CB) is involved in this effect. However, it remains poorly understood whether carbon monoxide (CO) also contributes to the altered peripheral chemoreflex sensitivity in CHF. This work highlights the effect of NO and CO on renal sympathetic nerve activity (RSNA) in response to graded hypoxia in conscious rabbits. Renal sympathetic nerve responses to graded hypoxia were enhanced in CHF rabbits compared with sham rabbits. The NO donor S-nitroso-N-acetylpenicillamine (SNAP, 1.2 microg x kg(-1) x min(-1)) and the CO-releasing molecule tricarbonyldichlororuthenium (II) dimer {[Ru(CO)(3)Cl(2)](2), 3.0 microg x kg(-1) x min(-1)} each attenuated hypoxia-induced RSNA increases in CHF rabbits (P < 0.05), but the degree of attenuation of RSNA induced by SNAP or [Ru(CO)(3)Cl(2)](2) was smaller than that induced by SNAP + [Ru(CO)(3)Cl(2)](2). Conversely, treatment with the NOS inhibitor N(omega)-nitro-L-arginine (30 mg/kg) + the heme oxygenase (HO) inhibitor Cr (III) mesoporphyrin IX chloride (0.5 mg/kg) augmented the renal sympathetic nerve response to hypoxia in sham rabbits to a greater extent than treatment with either inhibitor alone and was without effect in CHF rabbits. In addition, using immunostaining and Western blot analyses, we found that expression of neuronal NOS, endothelial NOS, and HO-2 protein (expressed as the ratio of NOS or HO-2 expression to beta-tubulin protein expression) was lower in CBs from CHF (0.19 +/- 0.04, 0.17 +/- 0.06, and 0.15 +/- 0.02, respectively) than sham (0.63 +/- 0.04, 0.56 +/- 0.06, and 0.27 +/- 0.03, respectively) rabbits (P < 0.05). These results suggest that a deficiency of NO and CO in the CBs augments peripheral chemoreflex sensitivity to hypoxia in CHF.     

Sulfite species enhance carbon monoxide release from CO-releasing molecules: implications for the deoxymyoglobin assay of activity

Carbon monoxide-releasing molecules (CO-RMs) emulate the beneficial (e.g., anti-inflammatory) effects of CO in biology. CO release from CO-RMs is routinely determined in the presence of reduced deoxy-myoglobin by measuring the formation of carboxy-myoglobin (Mb-CO). Previous studies have highlighted discrepancies between the apparent CO release rates of some CO-RMs established using this assay versus other experimental data where a slower or more complex mechanism of release is suggested. It has been hypothesized that some CO-RMs require a CO acceptor, believed to be reduced myoglobin in Mb-CO assays, in order to facilitate the release of CO. Here, we show, for the first time, that CO is not liberated from the ruthenium (Ru)-based [Ru(CO)(3)Cl(2)](2) (CORM-2) and [Ru(CO)(3)Cl(glycinate)] (CORM-3) at an appreciable rate in the presence of reduced myoglobin alone. Rather, we confirm that it is the reducing agent sodium dithionite that facilitates release of CO from these CO-RMs. Other sulfite compounds, namely sodium sulfite and potassium metabisulfite, also promote the liberation of CO from CORM-3. We describe an alternative oxy-hemoglobin assay that eliminates dithionite and suggest that the efficacy of CO-RMs results from intracellular interactions with anions that facilitate CO delivery to therapeutic targets.     

Structure, spectra and electrochemistry of ruthenium-carbonyl complexes of naphthylazoimidazole

[Ru(H)(CO)(PPh₃)₂(α/β-NaiR)](ClO₄) (3, 4) are synthesized by the reaction of [Ru(H)(Cl)(CO)(PPh₃)₃] with 1-alkyl-2-(naphthyl-α/β-azo)imidazole (α-NaiR (3); β-NaiR (4)). One of the complexes [Ru(H)(CO)(PPh₃)₂(α-NaiMe)](ClO₄) (3a) has been structurally established by X-ray diffraction study. Upon addition of Cl₂ saturated in MeCN to 3 or 4 gives [Ru(Cl)(CO)(α/β-NaiR)(PPh₃)₂](ClO₄) (for α-NaiR (5); β-NaiR (6)), without affecting metal oxidation state, which were characterized by spectroscopic measurements. The redox property of the complexes is examined by cyclic voltammetry.     

Heme oxygenase-1 signals are involved in preferential inhibition of pro-inflammatory cytokine release by surfactin in cells activated with Porphyromonas gingivalis lipopolysaccharide

Porphyromonas gingivalis is considered the major pathogen of periodontal disease, which leads to chronic inflammation in oral tissues. P. gingivalis-produced lipopolysaccharide (LPS) is a key factor in the development of periodontitis. It is established that surfactin produced by Bacillus subtilis confers anti-inflammatory properties. However, the underlying mechanisms responsible for surfactin-induced anti-inflammatory actions in the context of periodontitis are poorly understood. In this study, we investigated whether surfactin affected P. gingivalis LPS-induced pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-12, and determined that it significantly inhibited their production. Surfactin-mediated inhibition was mainly due to blocked activation of P. gingivalis LPS-triggered nuclear factor-κB. We also examined whether the regulatory effect of surfactin on P. gingivalis LPS-stimulated human THP-1 macrophages was mediated by the induction of heme oxygenase-1 (HO-1) signals, and determined that surfactin also induced HO-1 mRNA and protein expression via activation of Nrf-2. Additionally, we found that small interfering RNA-mediated knock-down of Nrf-2 significantly inhibited surfactin-induced HO-1 expression. Furthermore, inhibition of phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) significantly decreased surfactin-induced HO-1 expression, which is consistent with the suggestion that surfactin-induced HO-1 expression occurs via PI3K/Akt, ERK, and Nrf-2. Treatment with a selective inhibitor of HO-1 reversed the surfactin-mediated inhibition of pro-inflammatory cytokines, suggesting that surfactin induces anti-inflammatory effects by activating Nrf-2-mediated HO-1 induction via PI3K/Akt and ERK signaling. Collectively, these observations support the potential of surfactin as a candidate in strategies to prevent caries, periodontitis, or other inflammatory diseases.     

Highly efficient supramolecular photocatalysts for CO2 reduction using visible light.

We report the most efficient homogeneous photocatalyst yet for CO(2) reduction using a wide range of visible-light wavelength. We synthesized new Ru(II)-Re(I) binuclear complexes with 1,3-bis(4'-methyl-[2,2']bipyridinyl-4-yl)-propan-2-ol (bpyC3bpy) as a bridge ligand, specifically [Ru-ReP(OEt)(3)](3+) and [Ru-Repy](3+) where a P(OEt)(3) or pyridine ligand coordinates on the Re site. Their photocatalytic activities were compared with [Ru-ReCl](2+), which has a Cl(-) ligand on the Re site and has recently been reported as a much better photocatalyst (Phi = 0.12, TN(CO) = 160) than a 1:1 mixed system of the corresponding Ru(II) and Re(I) mononuclear complexes. The best photocatalyst was [Ru-ReP(OEt)(3)](3+), for which Phi = 0.21 and TN(CO) = 232. A mechanistic study clearly showed that [Ru-ReP(OEt)(3)](3+) is rapidly converted into the solvento complex [Ru-ReSol](3+), (Sol = DMF or TEOA) which is the actual photocatalyst. Although similar rapid ligand substitution occurs with other supramolecules, the pyridine and Cl(-) anions accelerate the decomposition of the supramolecular photocatalysts.     

DNA binding by Ru(II)–bis(bipyridine)–pteridinyl complexes

The interactions of five bis(bipyridyl) Ru(II) complexes of pteridinyl-phenanthroline ligands with calf thymus DNA have been studied. The pteridinyl extensions were selected to provide hydrogen-bonding patterns complementary to the purine and pyrimidine bases of DNA and RNA. The study includes three new complexes [Ru(bpy)(2)(L-pterin)](2+), [Ru(bpy)(2)(L-amino)](2+), and [Ru(bpy)(2)(L-diamino)](2+) (bpy is 2,2'-bipyridine and L-pterin, L-amino, and L-diamino are phenanthroline fused to pterin, 4-aminopteridine, and 2,4-diaminopteridine), two previously reported complexes [Ru(bpy)(2)(L-allox)](2+) and [Ru(bpy)(2)(L-Me(2)allox)](2+) (L-allox and L-Me(2)allox are phenanthroline fused to alloxazine and 1,3-dimethyalloxazine), the well-known DNA intercalator [Ru(bpy)(2)(dppz)](2+) (dppz is dipyridophenazine), and the negative control [Ru(bpy)(3)](2+). Reported are the syntheses of the three new Ru-pteridinyl complexes and the results of calf thymus DNA binding experiments as probed by absorption and fluorescence spectroscopy, viscometry, and thermal denaturation titrations. All Ru-pteridine complexes bind to DNA via an intercalative mode of comparable strength. Two of these four complexes-[Ru(bpy)(2)(L-pterin)](2+) and [Ru(bpy)(2)(L-allox)](2+)-exhibit biphasic DNA melting curves interpreted as reflecting exceptionally stable surface binding. Three new complexes-[Ru(bpy)(2)(L-diamino)](2+), [Ru(bpy)(2)(L-amino)](2) and [Ru(bpy)(2)(L-pterin)](2+)-behave as DNA molecular "light switches."     

Up-regulation of heme oxygenase-1 expression through the Rac1/NADPH oxidase/ROS/p38 signaling cascade mediates the anti-inflammatory effect of 15-deoxy-delta 12,14-prostaglandin J2 in murine macrophages

We investigated the signaling pathway that leads to the expression of heme oxygenase-1 (HO-1) in murine macrophages in response to 15-deoxy-delta 12,14-prostaglandin J2 (15dPGJ2). 15dPGJ2 caused dose- and time-dependent activation of Rac1, followed by a transient increase in reactive oxygen species (ROS) via NADPH oxidase, which leads to downstream activation of p38 kinase. Inhibition of 15dPGJ2-dependent HO-1 expression significantly attenuated suppression by 15dPGJ2 of LPS-induced iNOS expression and subsequent production of nitric oxide (NO). Our findings strongly suggest that 15dPGJ2 exerts its anti-inflammatory activity through the Rac1-NADPH oxidase-ROS-p38 signaling to the up-regulation of HO-1 in an in vitro inflammation model.     

Hydrogen sulfide inhibits nitric oxide production and nuclear factor-kappaB via heme oxygenase-1 expression in RAW264.7 macrophages stimulated with lipopolysaccharide

Hydrogen sulfide (H(2)S), a regulatory gaseous molecule that is endogenously synthesized by cystathionine gamma-lyase (CSE) and/or cystathionine beta-synthase (CBS) from L-cysteine (L-Cys) metabolism, is a putative vasodilator, and its role in nitric oxide (NO) production is unexplored. Here, we show that at noncytotoxic concentrations, H(2)S was able to inhibit NO production and inducible NO synthase (iNOS) expression via heme oxygenase (HO-1) expression in RAW264.7 macrophages stimulated with lipopolysaccharide (LPS). Both H(2)S solution prepared by bubbling pure H(2)S gas and NaSH, a H(2)S donor, dose dependently induced HO-1 expression through the activation of the extracellular signal-regulated kinase (ERK). Pretreatment with H(2)S or NaHS significantly inhibited LPS-induced iNOS expression and NO production. Moreover, NO production in LPS-stimulated macrophages that are expressing CSE mRNA was significantly reduced by the addition of L-Cys, a substrate for H(2)S, but enhanced by the selective CSE inhibitor beta-cyano-L-alanine but not by the CBS inhibitor aminooxyacetic acid. While either blockage of HO activity by the HO inhibitor, tin protoporphyrin IX, or down-regulation of HO-1 expression by HO-1 small interfering RNA (siRNA) reversed the inhibitory effects of H(2)S on iNOS expression and NO production, HO-1 overexpression produced the same inhibitory effects of H(2)S. In addition, LPS-induced nuclear factor (NF)-kappaB activation was diminished in RAW264.7 macrophages preincubated with H(2)S. Interestingly, the inhibitory effect of H(2)S on NF-kappaB activation was reversed by the transient transfection with HO-1 siRNA, but was mimicked by either HO-1 gene transfection or treatment with carbon monoxide (CO), an end product of HO-1. CO treatment also inhibited LPS-induced NO production and iNOS expression via its inactivation of NF-kappaB. Collectively, our results suggest that H(2)S can inhibit NO production and NF-kappaB activation in LPS-stimulated macrophages through a mechanism that involves the action of HO-1/CO.     

The protective role of localized nitric oxide production during inflammation may be mediated by the heme oxygenase-1/carbon monoxide pathway

Nitric oxide (NO) is an important part of the host defense mechanism; however, it displays both pro- and anti-inflammatory properties depending on its location and concentration. Importantly, excessive or inappropriate NO production can cause tissue damage. Systemic and local administration of NO synthase (NOS) inhibitors ameliorates and may exacerbate the inflammatory response, respectively. Here, we used a carrageenan-induced pleurisy model of acute inflammation in rats to confirm the location-dependent effects of NO and investigate the underlying mechanisms. As expected, localized suppression of NO production exacerbated inflammation, as evidenced by increased pleural exudate volumes and leukocyte counts and enhanced activity of enzymes related to oxidative stress. In contrast, local NO supplementation reduced leukocyte infiltration, vascular permeability, and the activity of oxidative stress-related enzymes. Interestingly, inhibition of heme oxygenase-1 (HO-1) reversed the anti-inflammatory effects of localized NO production, while the addition of hemin (HO-1 substrate) or carbon monoxide (CO; HO-1 metabolite) decreased leukocyte migration and exudation. Together, these findings confirm a protective role for NO at the inflammatory site, which appears to be mediated via NOS induction of the HO-1/CO pathway. Thus, NO supplementation may be a potential new treatment for oxidative stress-associated inflammatory diseases.