Dosing-time dependent effects of sodium nitroprusside on cerebral, renal, and hepatic catalase activity in mice

The Role of Oxidative and Nitrosative Stress of Silver Nanoparticles in Human Parasitic Helminth Brugia malayi: A Mechanistic Insight

PURPOSE

Silver nanoparticles (AgNPs) mediated apoptosis is well-known but its rationale is yet to be elucidated. This study explored the mechanistic underpinning of the apoptosis in the Brugia malayi parasitic model.

METHOD

Silver nanoparticles were synthesized and tested against B. malayi microfilariae (Mf) to explore the role of oxidative and nitrosative stress in its apoptotic effect.

RESULTS

AgNPs caused significant decrease in reduced glutathione (GSH) level and increase in both protein carbonylation and nitric oxide (NO) level indicating oxidative as well as nitrosative stress. Both GSH and nitric oxide synthase (NOS) inhibitors exhibited marked reversal. Nanoparticles and NO-donor in combination but not the NO-donor alone showed significant antiparasitic effect implying the requisite of combined oxidative and nitrosative stress to induce apoptosis. Synthetically prepared peroxynitrite from NaNO₂ to H₂O₂ showed marked antiparasitic effect in very low dose which could be achieved neither by NaNO₂ or H₂O₂ alone. GSH reversed the effect of peroxynitrite similar to its specific inhibitor, acetaminophen. GSH also reversed the plummet in mitochondrial oxygen consumption by AgNPs.

CONCLUSION

We conclude that apoptosis by AgNPs is possibly mediated through peroxynitrite dependent depletion of GSH; this provides a significant insight into the pharmacological as well as toxicological impact of AgNPs.

An electrochemical investigation into the effects of local and systemic administrations of sodium nitroprusside in brain extracellular fluid of mice

Sodium nitroprusside (SNP) is a nitric oxide (NO)-donor drug used clinically to treat severe hypertension, however, there are limitations associated with its mechanism of action that prevent widespread adoption. In particular, its impact on cerebral hemodynamics is controversial and direct evidence on its effects are lacking. Electrochemical methods provide an attractive option to undertake real time neurochemical measurements in situ using selective microsensors. Herein, we report the novel application of an existing platinum (Pt)-Nafion® sensor to measure the release of NO from SNP under in vitro and in vivo conditions. Initially, the temporal release of NO was measured and the effect of the reducing agent, ascorbic acid (AA), was elucidated in vitro. A combined microdialysis/NO sensor construct was implanted into the striatum of anaesthetised mice and the local perfusion of 10 mM SNP with/without AA resulted in increased NO concentration detected using the Pt-Nafion® sensor. Subsequently, the NO sensor, coupled with carbon paste electrodes (CPEs) for the electrochemical measurement of O₂, were applied to investigate SNP effects in freely moving mice. A complex mechanism of action was identified that infers NO inhibition and biphasic O₂ dynamics. The preliminary findings within support a strong cerebrovascular effect of systemic SNP administration that warrants careful consideration for clinical use.

Protective Effects of Selol Against Sodium Nitroprusside-Induced Cell Death and Oxidative Stress in PC12 Cells

Selol is an organic selenitetriglyceride formulation containing selenium at +4 oxidation level that can be effectively incorporated into catalytic sites of of Se-dependent antioxidants. In the present study, the potential antioxidative and cytoprotective effects of Selol against sodium nitroprusside (SNP)-evoked oxidative/nitrosative stress were investigated in PC12 cells and the underlying mechanisms analyzed. Spectrophoto- and spectrofluorimetic methods as well as fluorescence microscopy were used in this study; mRNA expression was quantified by real-time PCR. Selol dose-dependently improved the survival and decreased the percentage of apoptosis in PC12 cells exposed to SNP. To determine the mechanism of this protective action, the effect of Selol on free radical generation and on antioxidative potential was evaluated. Selol offered significant protection against the elevation of reactive oxidative species (ROS) evoked by SNP. Moreover, this compound restored glutathione homeostasis by ameliorating the SNP-evoked disturbance of GSH/GSSG ratio. The protective effect exerted by Selol was associated with the prevention of SNP-mediated down-regulation of antioxidative enzymes: glutathione peroxidase (Se-GPx), glutathione reductase (GR), and thioredoxin reductase (TrxR). Finally, GPx inhibition significantly abolished the cytoprotective effect of Selol. In conclusion, these results suggest that Selol effectively protected PC12 cells against SNP-induced oxidative damage and death by adjusting free radical levels and antioxidant system, and suppressing apoptosis. Selol could be successfully used in the treatments of diseases that involve oxidative stress and resulting apoptosis.