Nitric oxide releasing drugs: from bench to bedside

Nitric oxide-mediated the therapeutic properties of induced pluripotent stem cell for paraquat-induced acute lung injury

The mortality rate associated with acute lung injury (ALI) and its severe form, acute respiratory distress syndrome, is high. Induced pluripotent stem cell (iPSC) therapy is a potential treatment method for ALI, but its therapeutic efficacy is limited in injured lungs. Nitric oxide (NO) has various physiological actions. The current study investigated the effect of iPSCs pretreated with NO donors in paraquat (PQ)-induced ALI mouse model. Male C57BL/6 mice were intraperitoneally injected with PQ, followed by infusion of phosphate-buffered saline, iPSCs, L-arginine pretreated iPSCs, or Nitro-L-arginine methylester (L-NAME) pretreated iPSCs through the tail veins. Histopathological changes, pulmonary microvascular permeability, and inflammatory cytokine levels were analyzed after 3 or 28 d. The effects on iPSC proliferation, migration, and adhesion were evaluated in vitro. More L-arginine-pretreated iPSCs were selectively trafficked into the injured pulmonary tissue of mice with LPS-induced ALI, drastically diminishing the histopathologic changes and inflammatory cytokine levels (IL-1β and IL-6). There was also markedly improved pulmonary microvascular permeability and pulmonary function. The NO inhibitor abolished the protective effects of iPSCs. In addition, the ability of L-arginine to promote the proliferation and migration of iPSCs was decreased by L-NAME pretreatment, suggesting that NO might mediate the therapeutic benefits of iPSC. The improvement of the iPSC physiological changes by the endogenous gaseous molecule NO reduces lung injury severity. L-Arginine represents a pharmacologically important strategy for enhancing the therapeutic potential of iPSCs.

Vasorelaxant Effect of Novel Nitric Oxide-Hydrogen Sulfide Donor Chalcone in Isolated Rat Aorta: Involvement of cGMP Mediated sGC and Potassium Channel Activation

BACKGROUND AND OBJECTIVE

Recently, nitric oxide (NO) and hydrogen sulfide (H2S) donating moieties were extensively studied for their role in the vasculature as they are responsible for many cellular and pathophysiological functioning. The objective of the present study is to evaluate novel NO and H2S donating chalcone moieties on isolated rat aorta for vasorelaxation, and to investigate the probable mechanism of action.

METHODS

To extend our knowledge of vasorelaxation by NO and H2S donor drugs, here we investigated the vasorelaxing activity of novel NO and H2S donating chalcone moieties on isolated rat aorta. The mechanism of vasorelaxation by these molecules was investigated by performing in vitro cGMP mediated sGC activation assay and using Tetraethylammonium chloride (TEA) as a potassium channel blocker and Methylene blue as NO blocker.

RESULTS

Both NO and H2S donating chalcone moieties were found to be potent vasorelaxant. The compound G4 and G5 produce the highest vasorelaxation with 3.716 and 3.789 M of pEC50, respectively. After the addition of TEA, G4 and G5 showed 2.772 and 2.796 M of pEC50, respectively. The compounds Ca1, Ca2, and D7 produced significant activation and release of cGMP mediated sGC which was 1.677, 1.769 and 1.768 M of pEC50, respectively.

CONCLUSION

The vasorelaxation by NO-donating chalcones was blocked by Methylene blue but it did not show any effect on H2S donating chalcones. The vasorelaxing potency of NO-donating molecules was observed to be less affected by the addition of TEA but H2S donors showed a decrease in both efficacy and potency. The cGMP release was more in the case of NO-donating molecules. The tested compounds were found potent for relaxing vasculature of rat aorta.

Notoginsenoside Ft1 activates both glucocorticoid and estrogen receptors to induce endothelium-dependent, nitric oxide-mediated relaxations in rat mesenteric arteries

Panax notoginseng (Burk.) F.H. Chen has been used traditionally for the treatment of cardiovascular diseases. Notoginsenoside Ft1 (Ft1) is a bioactive saponin from the leaves of P. notoginseng. Experiments were designed to determine whether or not Ft1 is an endothelium-dependent vasodilator. Rat mesenteric arteries were suspended in organ chambers for the measurement of isometric tension during phenylephrine-induced contractions. The cyclic guanosine monophosphate (cGMP) level was assessed using enzyme immunoassay. The phosphorylation and protein expressions of endothelial nitric oxide synthase (eNOS), glucocorticoid receptors (GR), estrogen receptors beta (ERß), protein kinase B (Akt) and extracellular signal-regulated kinase 1/2 (ERK1/2) were determined by Western blotting. The localization of GR and ERß were determined by immunofluorescence staining. Ft1 caused endothelium-dependent relaxations, which were abolished by l-NAME (inhibitor of nitric oxide synthases) and ODQ (inhibitor of soluble guanylyl cyclase). Ft1 increased the cGMP level in rat mesenteric arteries. GR and ERß were present in the endothelial layer and their antagonism by RU486 and PHTPP, respectively, inhibited Ft1-induced endothelium-dependent relaxations and phosphorylations of eNOS, Akt and ERK1/2. Inhibition of phosphoinositide-3-kinase (PI3K) by wortmannin and ERK1/2 by U0126 reduced Ft1-evoked relaxations and eNOS phosphorylation. Taken in conjunction, the present findings suggest that Ft1 stimulates endothelial GRs and ERßs with subsequent activation of the PI3K/Akt and ERK1/2 pathways in rat mesenteric arteries. This results in phosphorylation of eNOS and the release of NO, which activates soluble guanylyl cyclase in the vascular smooth muscle cells leading to relaxations.

Apoptosis of hepatic stellate cells (HSC-T6) induced by sodium nitroprusside and mechanisms involved

AIM: To investigate whether nitric oxide (NO) donor sodium nitroprusside (SNP) can induce the apoptosis of hepatic stellate cells (HSC-T6) and to explore potential mechanisms involved.

METHODS: The apoptosis of HSC-T6 cells was determined by flow cytometry and Hoechst staining. The nuclear translocation of nuclear factor-κB (NF-κB) p65 was detected by laser scanning confocal microscopy. The expression of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), type I procollagen (procollagen I), and growth arrest and DNA damage-inducible protein (GADD45β) mRNAs was detected by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: The apoptosis rate was significantly higher in HSC-T6 cells treated with SNP than in control cells (20.78% ± 5.91%vs 3.25% ± 1.26%, P = 0.031). Apoptotic HSC-T6 cells showed dense nuclear staining or granular fluorescence after Hoechst staining. Tumor necrosis factor-α (TNF-α)-mediated nuclear translocation of NF-κB p65 was inhibited by SNP treatment. With the increase in SNP dose, the expression levels of TIMP-1, procollagen I and GADD45β mRNAs were reduced (all P < 0.05).

CONCLUSION: SNP can induce the apoptosis of HSC-T6 cells and reduce the expression of TIMP-1 and procollagen I mRNAs perhaps by inhibiting NF-κB activity and reducing GADD45β mRNA expression.

Platelet aggregation is affected by nitrosothiols in patients with chronic hepatitis: In vivo and in vitro studies

AIM: To investigate the relationship among the number of platelets and plasma levels of S-nitrosothiols (S-NO), nitrite, total non-protein SH (NPSH), glutathione (GSH), cysteine (CYS), malondialdehyde (MDA), 4-hydroxininenal (4HNE), tumor necrosis factor-alpha (TNFα) and interleukin (IL)-6 in patients with chronic hepatitis C (CH).

METHODS: In vitro the aggregation of platelets derived from controls and CH patients was evaluated before and after the addition of adenosine diphosphate (ADP) and collagen, both in basal conditions and after incubation with nitrosoglutathione (GSNO).

RESULTS: In vivo, S-NO plasma levels increased significantly in CH patients and they were significantly directly correlated with platelet numbers. Patients with platelet counts < 150 000/μL, had a smaller increase in S-NO, lower levels of GSH, CYS, NPSH, TNFα, and IL-6, and higher levels of nitrite, MDA, and 4-HNE relative to those of patients with platelet counts > 150 000/μL. In vitro, the ADP and collagen aggregation time was increased in platelets from patients and not from controls; in addition, platelets from CH patients but not from controls also showed a latency time after exposure to collagen.

CONCLUSION: The incubation of platelets with GSNO improved the percentage aggregation and abolished the latency time.

Growth hormone regulates intestinal ion transport through a modulation of the constitutive nitric oxide synthase-nitric oxide-cAMP pathway

AIM: Growth hormone (GH) directly interacts with the enterocyte stimulating ion absorption and reducing ion secretion induced by agonists of cAMP. Since nitric oxide (NO) is involved in the regulation of transepithelial ion transport and acts as a second messenger for GH hemodynamic effects, we tested the hypothesis that NO may be involved in the resulting effects of GH on intestinal ion transport.

METHODS: Electrical parameters reflecting trans-epithelial ion transport were measured in Caco-2 cell monolayers mounted in Ussing chambers and exposed to GH and cholera toxin (CT) alone or in combination, in the presence or absence of the NO synthase (NOS) inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME). Similar experiments were conducted to determine cAMP and nitrite/nitrate concentrations. NOS expression was assayed by Western blot analysis.

RESULTS: L-NAME causes total abrogation of absorptive and anti-secretory effects by GH on intestinal ion transport. In addition, L-NAME was able to inhibit the GH-effects on intracellular cAMP concentration under basal conditions and in response to CT. GH induced a Ca²⁺-dependent increase of nitrites/nitrates production, indicating the involvement of the constitutive rather than the inducible NOS isoform, which was directly confirmed by Western blot analysis.

CONCLUSION: These results suggest that the GH effects on intestinal ion transport, either under basal conditions or in the presence of cAMP-stimulated ion secretion, are mediated at an intracellular level by the activity of cNOS.

Nitric oxide (NO)-releasing naproxen (HCT-3012 [(S)-6-methoxy-alpha-methyl-2-naphthaleneacetic Acid 4-(nitrooxy)butyl ester]) interactions with aspirin in gastric mucosa of arthritic rats reveal a role for aspirin-triggered lipoxin, prostaglandins, and NO in gastric protection

Administration of selective and nonselective cyclooxygenase (COX)-2 inhibitors to rheumatoid arthritis patients taking low doses of acetylsalicylic acid (ASA) for cardiovascular prevention associates with increased risk of gastrointestinal bleeding. The present study was undertaken to investigate whether administration of HCT-3012 [(S)-6-methoxy-alpha-methyl-2-naphthaleneacetic acid 4-(nitrooxy)butyl ester], a nitric oxide (NO)-releasing derivative of naproxen, exacerbates gastric mucosal injury in arthritic rats administered low doses of ASA. Our results demonstrated that while treating arthritic rats with a dose of 30 mg/kg/day ASA causes detectable mucosal injury, but had no effect on arthritis score and interleukin-6 plasma levels, coadministration of naproxen (10 mg/kg/day) and celecoxib (30 mg/kg/day), in combination with ASA from day 7 to day 21, attenuates arthritis development (P <0.01 versus arthritis alone), but markedly enhanced gastric mucosal damage caused by ASA (P <0.01 versus ASA alone). In contrast, coadministration of HCT-3012 (15 mg/kg/day) significantly attenuated arthritis development, because HCT-3012 was equally or more effective than naproxen and celecoxib in attenuating local and systemic inflammation (P >0.001 versus arthritis) without exacerbating gastric mucosal injury caused by ASA. Arthritis development associates with gastric COX-2 induction, mRNA and protein, and enhanced gastric prostaglandin E2 (PGE2) synthesis (P <0.01 versus control rats). Although all treatments, including celecoxib, were effective in reducing gastric PGE2 synthesis, administering arthritic rats with ASA resulted in a significant increase in gastric content of aspirin-triggered lipoxin (ATL), a COX-2-derived lipid mediator that regulates proinflammatory responses at the neutrophils/endothelial interface. Administering arthritic rats with naproxen and celecoxib abrogates ATL formation induced by ASA although enhanced neutrophils accumulate into the gastric mucosa (P <0.01 versus ASA alone). In contrast, whereas HCT-3012 inhibited ATL formation, it did not increase neutrophil recruitment into the gastric microcirculation. Collectively, these data indicate that HCT-3012 derived from NO has the potential to compensate for inhibition of PGE2 and ATL and to protect the gastric mucosa by limiting the recruitment of neutrophils. These data suggest that HCT-3012 might be a safer alternative to nonsteroidal anti-inflammatory drugs and coxibs in rheumatic patients that take low doses of ASA.