Anna Sparatore

Pharmacological profile of a novel H2S-releasing aspirin

The pharmacological profile of a new, safe, and effective hydrogen sulfide (H(2)S)-releasing derivative of aspirin (ACS14) is described. We report the synthesis of ACS14, and of its deacetylated metabolite (ACS21), the preliminary pharmacokinetics, and its in vivo metabolism, with the H(2)S plasma levels after intravenous administration in the rat. ACS14 maintains the thromboxane-suppressing activity of the parent compound, but seems to spare the gastric mucosa, by affecting redox imbalance through increased H(2)S/glutathione formation, heme oxygenase-1 promoter activity, and isoprostane suppression.

Exogenous Hydrogen Sulfide Inhibits Superoxide Formation, NOX-1 Expression and Rac1 Activity in Human Vascular Smooth Muscle Cells

The activity of NADPH oxidase (NOX) is blocked by nitric oxide (NO). Hydrogen sulfide (H₂S) is also produced by blood vessels. It is reasonable to suggest that H₂S may have similar actions to NO on NOX. In order to test this hypothesis, the effect of sodium hydrosulfide (NaHS) on O₂^– formation, the expression of NOX-1 (a catalytic subunit of NOX) and Rac₁ activity (essential for full NOX activity) in isolated vascular smooth muscle cells (hVSMCs) was investigated. hVSMCs were incubated with the thromboxane A₂ analogue U46619 ± NaHS for 1 or 16 h, and O₂^– formation, NOX-1 expression and Rac₁ activity were assessed. The possible interaction between H₂S and NO was also studied by using an NO synthase inhibitor, L-NAME, and an NO donor, DETA-NONOate. The role of K_ATP channels was studied by using glibenclamide. NaHS inhibited O₂^– formation following incubation of 1 h (IC₅₀, 30 nM) and 16 h (IC₅₀, 20 nM), blocked NOX-1 expression and inhibited Rac₁ activity. These inhibitory effects of NaHS were mediated by the cAMP-protein-kinase-A axis. Exogenous H₂S prevents NOX-driven intravascular oxidative stress through an a priori inhibition of Rac₁ and downregulation of NOX-1 protein expression, an effect mediated by activation of the adenylylcyclase-cAMP-protein-kinase-G system by H₂S.

H2S-donating sildenafil (ACS6) inhibits superoxide formation and gp91phox expression in arterial endothelial cells: role of protein kinases A and G

Superoxide (O2•−), derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, is associated with acute respiratory distress syndrome (ARDS). NADPH oxidase activity and expression are blocked by nitric oxide (NO) and sildenafil. As another gas, hydrogen sulphide (H2S) is formed by blood vessels, the effect of sodium hydrosulphide (NaHS) and the H2S‐donating derivative of sildenafil, ACS6, on O2•− formation and the expression of gp91phox (a catalytic subunit of NADPH oxidase) in porcine pulmonary arterial endothelial cells (PAECs) was investigated.

Modulation of angiogenesis by dithiolethione‐modified NSAIDs and valproic acid

Angiogenesis involves multiple signaling pathways that must be considered when developing agents to modulate pathological angiogenesis. Because both cyclooxygenase inhibitors and dithioles have demonstrated anti‐angiogenic properties, we investigated the activities of a new class of anti‐inflammatory drugs containing dithiolethione moieties (S‐NSAIDs) and S‐valproate.

Hydrogen sulfide-releasing NSAIDs attenuate neuroinflammation induced by microglial and astrocytic activation.

Endogenously generated hydrogen sulfide (H2S) may have multiple functions in brain. It has been shown that H2S attenuates the expression of pro‐inflammatory cytokines by lipopolysaccharide (LPS)‐activated microglia. Here we demonstrate a neuroprotective effect of NaSH and three H2S‐releasing compounds, ADT‐OH, S‐diclofenac, and S‐aspirin. When activated by LPS and γ‐interferon, human microglia and THP‐1 cells release materials that are toxic to human neuroblastoma SH‐SY5Y cells. These phenomena also occur with γ‐interferon‐stimulated human astroglia and U118 cells. When these cell types are pretreated with aspirin, diclofenac, NASH, or ADT‐OH, the supernatants are significantly less toxic. When they are treated with the NSAID‐H2S hybrid molecules S‐diclofenac and S‐aspirin, which are here referred to as S‐NSAIDs, there is a significant enhancement of the protection. The effect is concentration and incubation time dependent. Such pretreatment also reduces the release of the proinflammatory mediators TNFα, IL‐6, and nitric oxide. The H2S‐releasing compounds are without effect when applied directly to SH‐SY5Y cells. These data suggest that hybrid H2S releasing compounds have significant antiinflammatory properties and may be candidates for treating neurodegenerative disorders that have a prominent neuroinflammatory component such as Alzheimer disease and Parkinson disease.

The hydrogen sulphide-releasing derivative of diclofenac protects against ischaemia–reperfusion injury in the isolated rabbit heart

Hydrogen sulphide (H2S) is an endogenous gaseous mediator active in the multilevel regulation of pathophysiological functions in mammalian cardiovascular tissues.

Effect of hydrogen sulphide-donating sildenafil (ACS6) on erectile function and oxidative stress in rabbit isolated corpus cavernosum and in hypertensive rats

To study the effect of the H2S‐donating derivative of sildenafil (ACS6) compared to sildenafil citrate and sodium hydrosulphide (NaHS) on relaxation, superoxide formation and NADPH oxidase and type 5 phosphodiesterase (PDE5) expression in isolated rabbit cavernosal tissue and smooth muscle cells (CSMCs), and in vivo on indices of oxidative stress induced with buthionine sulphoximine (BSO).

Effects of hydrogen sulfide-releasing L-DOPA derivatives on glial activation: potential for treating Parkinson disease

The main lesion in Parkinson disease (PD) is loss of substantia nigra dopaminergic neurons. Levodopa (l-DOPA) is the most widely used therapy, but it does not arrest disease progression. Some possible contributing factors to the continuing neuronal loss are oxidative stress, including oxidation of l-DOPA, and neurotoxins generated by locally activated microglia and astrocytes. A possible method of reducing these factors is to produce l-DOPA hybrid compounds that have antioxidant and antiinflammatory properties. Here we demonstrate the properties of four such l-DOPA hybrids based on coupling l-DOPA to four different hydrogen sulfide-donating compounds. The donors themselves were shown to be capable of conversion by isolated mitochondria to H2S or equivalent SH− ions. This capability was confirmed by in vivo results, showing a large increase in intracerebral dopamine and glutathione after iv administration in rats. When human microglia, astrocytes, and SH-SY5Y neuroblastoma cells were treated with these donating agents, they all accumulated H2S intracellularly as did their derivatives coupled to l-DOPA. The donating agents and the l-DOPA hybrids reduced the release of tumor necrosis factor-α, interleukin-6, and nitric oxide from stimulated microglia, astrocytes as well as the THP-1 and U373 cell lines. They also demonstrated a neuroprotective effect by reducing the toxicity of supernatants from these stimulated cells to SH-SY5Y cells. l-DOPA itself was without effect in any of these assays. The H2S-releasing l-DOPA hybrid molecules also inhibited MAO B activity. They may be useful for the treatment of PD because of their significant antiinflammatory, antioxidant, and neuroprotective properties.

Effect of S-diclofenac, a novel hydrogen sulfide releasing derivative inhibit rat vascular smooth muscle cell proliferation

S-diclofenac (2-[(2,6-dichlorophenyl) amino] benzene acetic acid 4-(3H-1,2,dithiol-3-thione-5-yl) phenyl ester) is a novel molecule comprising a hydrogen sulfide (H2S)-releasing dithiol-thione moiety attached by an ester linkage to diclofenac. Effect of S-diclofenac (H2S donor) on cell proliferation was investigated on the primary and immortalized rat aortic vascular smooth muscle cells (SMC). Smooth muscle cell proliferation has been considered as a key event in vascular injury in diseases such as atherosclerosis and restenosis after invasive intervention. Clonogenic cell survival assay showed a dose dependent (10-100 microM) decrease in cell survival. Flow cytometric analysis showed that the asynchronized cells are more sensitive than the cells that are synchronized and revealed that the cells in G1 phase are not affected by the treatment of the S-diclofenac. Asynchronized smooth muscle cells treated with the S-diclofenac showed an increase in apoptotic cell death. S-diclofenac treatment also resulted in stabilization of p53 coupled with the induction of downstream proteins such as p21, p53AIP1 and Bax. S-diclofenac did not up-regulate cell levels of the antiapoptotic protein Bcl-2. However, when the cells are synchronized a stimulatory effect of cell growth with the decrease in apoptosis, p53 and p21 was evident. S-diclofenac inhibits smooth muscle cell growth and may play a role in the lesion formation at sites of the vascular injury. The present results suggest that S-diclofenac may be useful for the prevention of smooth muscle cell proliferation in diseases such as vascular obstructive and restenosis.

Therapeutic potential of new hydrogen sulfide-releasing hybrids

A new class of hydrogen sulfide (H2S)-donating hybrids combined with pharmacologically active compounds is presented in this article. The pharmacological profiles of some hybrid lead compounds in the areas of inflammation, H2S-donating diclofenac (ACS 15); cardiovascular, H2S-donating aspirin (ACS 14); urology, H2S-donating sildenafil (ACS 6); and neurodegenerative, H2S-donating latanoprost (ACS 67) for glaucoma treatment and H2S-donating levodopa (ACS 84) for Parkinson’s disease, are described. The new H2S-releasing hybrids demonstrate remarkable improvement in activity and tolerability as compared with the related parent compounds, suggesting an active pharmacological role for H2S. Finally the mechanism(s) of action of glutathione-dependent and independent, and of gas (H2S) release (spontaneous or enzymatic) and its implications for clinical pharmacology perspectives will be also discussed.