Sodium azide dilates coronary arterioles via activation of inward rectifier K+ channels and Na+-K+-ATPase

Activation of Smooth Muscle Kir2.1 Channels and Na+/K+-ATPase Mediates Dilation of Porcine Coronary Arterioles at Physiological Levels of Potassium

Metabolic stress on the heart can cause dilation of coronary arterioles for blood flow recruitment. Although potassium ions (K+) released from the myocardium are a major mediator for this response, the underlying signaling pathways for vasodilation are incompletely understood. Herein, the roles of smooth muscle inward-rectifier K+ channel subtype 2.1 (Kir2.1) and Na+/K+-ATPase were examined. Porcine coronary arterioles were isolated, cannulated, and pressurized for vasomotor study. Vessels developed basal tone and dilated concentration-dependently to extraluminal K+ from 7 to 20 mM. Higher K+ concentrations (25-40 mM) caused graded vasoconstriction. Vasodilation to K+ (10 mM) was not altered by endothelial removal, and blockade of ATP-sensitive K+ channels, voltage-sensitive K+ channels, or calcium-activated K+ channels did not affect K+-induced vasodilation. However, sustained but not abrupt transient vasodilation to K+ was reduced by the nonspecific Kir channel inhibitor Ba2+ or Kir2.1 channel blocker chloroethylclonidine. The Na+/K+-ATPase inhibitor ouabain attenuated K+-elicited vasodilation, and ouabain with Ba2+ abolished the response. Transfection of arterioles with Kir2.1 antisense oligonucleotides abolished sustained but not transient dilation. It is concluded that extraluminal K+ elevation within the physiological range induces initial transient dilation of porcine coronary arterioles by activating smooth muscle Na+/K+-ATPase and sustained dilation via smooth muscle Kir2.1 channels.

Zinc and ascorbic acid treatment alleviates systemic inflammation and gastrointestinal and renal oxidative stress induced by sodium azide in rats

Background

Sodium azide (NaN3) is a chemical of rapidly increasing economic importance but with high toxic attributes. In this study, the effects of zinc (Zn) and ascorbic acid (AsA) supplementation on sodium azide (NaN3)-induced toxicity in the stomach, colon and kidneys were evaluated in Wistar rats. Twenty-eight rats were randomly allocated to four experimental groups as follows: group A (control) given distilled water only; group B (NaN3 only, 20 mg/kg); group C (NaN3 + zinc sulphate, ZnSO4 80 mg/kg); and group D (NaN3 + AsA 200 mg/kg).

Results

NaN3 was found to significantly (p < 0.05) induce increases in serum nitric oxide (NO), advanced oxidation protein products (AOPP), myeloperoxidase (MPO) and total protein levels, along with significant (p < 0.05) increase in gastric, colonic and renal malondialdehyde (MDA) and protein carbonyl (PCO) levels. In addition, NaN3 induced significant (p < 0.05) reduction in superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities in the colon and kidneys. Treatment with Zn or AsA caused significant (p < 0.05) reduction in serum levels of oxidative and inflammatory markers, as well as tissue PCO and MDA levels. Moreover, co-treatment with Zn or AsA significantly (p < 0.05) restored colonic and renal levels of antioxidant enzymes, reduced glutathione and protein thiols.

Conclusions

This study shows that Zn or AsA supplementation alleviated  NaN3 toxicity by suppressing systemic inflammation and preventing oxidative damage in the stomach, colon and kidneys of rats.

Study of Mental Illness in Rat Model of Sodium Azide Induced Oxidative Stress

Aim: Oxidative stress is known as Reactive oxygen species (ROS) accumulation that is caused by reactive ROS and antioxidants imbalance that could be due to decreased antioxidant levels. Oxidative stress is often related to aging, Oxygen metabolism and redox imbalance in cells and tissues. It is a cellular state in which oxidants levels e.g. superoxide (O-2), hydrogen peroxide (H2O2) or nitric oxide (NO) in biological metabolisms exceed the oxidants scavenging capacity of cells. Oxidative stress in brain leads to depression, anxiety, memory impairment and behavioral deficits associated with them. Method: 24 male albino wistar rats were allocated into test and controls groups administered with sodium azide (5 mg/kg bodyweight) (i.p.) and water (p.o.) respectively for 14 days. Behaviors were monitored weekly after 24 hours of sodium azide administration in light/dark box, elevated plus maze, Open field and Morris water maze. Results: Test animals that were administered with sodium azide significantly decreased entries and time spent in illuminated area of light dark box and elevated plus maze while increased latency and fewer square crossed were observed with decreased learning acquisition and memory retention. Conclusion: All the data collected and results analysis determine oxidative stress could cause mood disorders learning disabilities. Sodium azide induced oxidative stress produce behavioral deficits and memory impairment validated it as a neurotoxin.

Blue light negatively affects the survival of ARPE19 cells through an action on their mitochondria and blunted by red light

PURPOSE

To ascertain whether red light, known to enhance mitochondrial function, can blunt a blue light insult to ARPE19 cells in culture.

METHODS

Semi-confluent ARPE19 cells cultured in 10% FBS were subjected to various regimes of treatment with blue (465-475 nm, 800 lux, 26 W/m² ) and red (625-635 nm, 950 lux, 6.5 W/m² ) light, as well as with toxins that inactivate specific enzymes associated with mitochondrial oxidative phosphorylation. Cultures were then analysed for cell viability (MTT assay), mitochondrial status (JC-1), ROS formation, immunocytochemistry and the activation of specific proteins by electrophoresis/Western blotting. In addition, ARPE19 cells were cultured in polycarbonate membrane inserts in culture medium containing 1% FBS. Such cultures were exposed to cycles of red, blue or a combination of red and blue light for up to 6 weeks. Culture medium was changed and the trans-epithelium membrane resistance (TER) of the inserts-containing cells was measured twice weekly.

RESULTS

ARPE19 cells in culture are affected negatively when exposed to blue light. This is indicated by a loss of viability, a depolarization of their mitochondria and a stimulation of ROS. Moreover, blue light causes an up-regulation of HO-1 and phospho-p-38-MAPK and a cleavage of apoptosis inhibitory factor, proteins which are all known to be activated during cell death. All of these negative effects of blue light are significantly blunted by the red light administered after the blue light insult in each case. ARPE19 cell loss of viability and mitochondrial potential caused by toxins that inhibit specific mitochondrial enzyme complexes was additive to an insult delivered by blue light in each case. After a time, ARPE19 cells in culture express the tight junction protein ZO-1, which is affected by blue light. The development of tight junctions between ARPE19 cells grown in inserts reached a steady peak of resistance after about 40 days and then increased very slightly over the next 40 days when still in darkness. However, maximum resistance was significantly attenuated, when cultures were treated with cycles of blue light after the initial 40 days in the dark and counteracted significantly when the blue light cycle insult was combined with red light.

CONCLUSION

Blue light affects mitochondrial function and also the development tight junctions between ARPE19 cells, which results in a loss of cell viability. Importantly, red light delivered after a blue light insult is significantly blunted. These findings argue for the therapeutic use of red light as a noninvasive procedure to attenuate insults caused by blue light and other insults to retinal pigment epithelial cell mitochondria that are likely to occur in age-related macular degeneration.

Mdivi‑1 attenuates sodium azide‑induced apoptosis in H9c2 cardiac muscle cells

The aim of the current study was to investigate the effect of mitochondrial division inhibitor 1 (Mdivi-1) in sodium azide-induced cell death in H9c2 cardiac muscle cells. Mdivi-1 is a key inhibitor of the mitochondrial division protein dynamin-related protein 1 (Drp1). Mdivi-1 was added to H9c2 cells for 3 h, after which, the cells were treated with sodium azide for 24 h. Cell viability was measured by Cell Counting kit-8 assay. DAPI staining was used to observe nuclear morphology changes by microscopy. To further investigate the role of mitochondria in sodium azide-induced cell death, mitochondrial membrane potential (ΔΨm) and the cellular ATP content were determined by JC-1 staining and ATP-dependent bioluminescence assay, respectively. Reactive oxygen species (ROS) production was also assessed by use of the specific probe 2′,7′-dichlorodihydrofluorescein diacetate. In addition, the expression of Drp1 and of the apoptosis-related proteins BCL2 apoptosis regulator (Bcl-2), and BCL2 associated X (Bax) was determined by western blotting. The present findings demonstrated that pretreatment with Mdivi-1 attenuated sodium azide-induced H9c2 cell death. Mdivi-1 pretreatment also inhibited the sodium azide-induced downregulation of Bcl-2 expression and upregulation of Bax and Drp1 expression. In addition, the mitochondrion was revealed to be the target organelle of sodium azide-induced toxicity in H9c2 cells. Mdivi-1 pretreatment moderated the dissipation of ΔΨm, preserved the cellular ATP contents and suppressed the production of ROS. The results suggested that the mechanism of sodium azide-induced cell death in H9c2 cells may involve the mitochondria-dependent apoptotic pathway. The present results indicated that Mdivi-1 may have a cardioprotective effect against sodium azide-induced apoptosis in H9c2 cardiac muscle cells.

Ameliorative effect of vitamin E and selenium against oxidative stress induced by sodium azide in liver, kidney, testis and heart of male mice

The study purported to define the effects of daily administration of vitamin E (Vit E) and selenium (Se) on antioxidant enzyme activity in mice treated with high doses of sodium azide (SA). Male mice were randomly split into nine groups. Groups 1, 2 and 3 were injected daily with saline, Vit E, and Se, respectively, while groups 4, 5 and 6 administrated with different doses of SA (low, medium and high, respectively). The mice in groups 7, 8 and 9 received 100mg/kg Vit E, 17.5mg/kg Se, and a combination of Vit E and Se, respectively before the SA-treatment. Hepatic, renal, testis and heart, antioxidant enzymes as well as levels of lipid peroxidation and total antioxidant capacity levels were determined. Vit E alone affected on the antioxidant parameters of the examined tissues. Se had a preventive effect on the decrease of antioxidant parameters caused by SA and improved the diminished activities of all of them. The study demonstrates that a high dose of SA may alter the effects of normal level antioxidant/oxidative status of male mice and that Se is effective in reducing the SA-damage. Se acts as a synergistic agent with the effect of Vit E in various damaged caused by SA.

Sodium azide suppresses LPS-induced expression MCP-1 through regulating IκBζ and STAT1 activities in macrophages

Sodium azide (NaN₃) is a chemical compound with multiple toxic effects on vascular and neuronal systems, causing hypotension and neurotoxicity, respectively. In order to test its effects on the immune system, human and mouse macrophage-like cell lines were treated with nontoxic doses of NaN₃ and the changes in LPS-induced inflammatory activation was measured. Interestingly, the LPS-induced expression of monocyte chemoattractant protein (MCP)-1 was suppressed by NaN₃ without affecting the expression of IL-8 and TNF-α. Further analysis of cellular signaling mediators involved in the expression of these cytokines revealed that NaN₃ suppressed the LPS-induced activation of signal transducers and activator of transcription (STAT)1 and inhibitor of κB (IκB) ς, which are involved in the LPS-induced expression of MCP-1, while the LPS-induced activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) was not affected. The LPS-induced expression of MCP-2 and CXCL10, which are also regulated by STAT1, was suppressed by NaN₃. Similarly, the LPS-induced expression of IL-6, which is regulated by IκBζ, was suppressed by NaN₃. These results demonstrate that NaN₃ selectively suppresses the LPS-induced expression of pro-inflammatory mediators through the suppression of STAT1 and IκBζ activation. These new findings about the activity of NaN₃ may contribute to the development of specific regulators of macrophage activity during acute and chronic inflammation.

Temperature increase exacerbates apoptotic neuronal death in chemically-induced ischemia

It is well-established that hyperthermia increases neuronal death and worsens stroke outcome. However, little is known about the mechanisms of how hyperthermia is involved in this neuronal death process. In the present study, we examined how temperature increase exacerbates neuronal death using a model of chemical ischemia. Chemical ischemia was induced by treating SH-SY5Y neuroblastoma cells with sodium azide and deoxyglucose. Temperature increase was treated by placing the cells at 37°C (control) and 41°C (experimental). Cell survival was determined by trypan blue assay and ATP levels were measured with ATP assay kits. Protein expression was detected by western blot. Treatment with sodium azide resulted in cell death in a dose-responsive manner. Increased temperature worsened the ATP depletion and cell volume shrinkage. Temperature increase also enhanced ER stress as demonstrated by the elevated level of phospho-eIF2α and C/EBP homologous protein (CHOP). Inhibition of CHOP expression significantly decreased sodium azide-induced neuronal death. In addition, the increased temperature intensified the activation of caspase-3, an apoptotic effector protease, and inhibition of capspase-3 significantly reduced cell death. These findings support that temperature increase worsened the neuronal death by depleting intracellular ATP, inducing ER stress response and activating apoptotic signal transduction.

Maternal and developmental toxicity study of sodium azide in rats

Sodium azide (NaN(3)) is being proposed for use as an active ingredient to control a broad spectrum of soil borne pathogens including insects, weeds, nematodes, fungi, and bacteria. The purpose of this study was to determine the maternal and developmental toxicity of NaN(3) in rats. Sperm-positive Sprague-Dawley rats were treated with NaN(3) via oral gavage once daily from Gestation Day (GD) 6 through 19 at respective dose levels of 0, 1, 5, and 17.5mg/kg/day. From GD 10-12, the high-dose was reduced to 10mg/kg/day due to maternal mortality. Cesarean section was performed on GD 20 and implantation and resorptions sites, live and dead fetuses were counted. Fetuses were weighed, sexed externally and processed for gross external, visceral and skeletal examinations. A high rate of maternal mortality; reduced gestation body weight, gestation body weight changes and food consumption; decreased corrected body weight and corrected weight gain were observed at 17.5/10mg/kg/day. Fetal weight was also reduced at 17.5/10mg/kg/day. There were no maternal deaths, clinical signs or body weight effects that were considered related to NaN(3) at 1 and 5mg/kg/day. No increase in the incidence of malformations and variations were observed at any of the doses evaluated. Based on the results of this study, the No Observed Adverse Effect Level (NOAEL) and the Lowest Observed Adverse Effect Level (LOAEL) for maternal and developmental toxicity of NaN(3) in rats were considered to be 5 and 17.5/10mg/kg/day, respectively.

Sodium azide, a bacteriostatic preservative contained in commercially available laboratory reagents, influences the responses of human platelets via the cGMP/PKG/VASP pathway

OBJECTIVE

The bacteriostatic preservative sodium azide (NaN(3)) activates soluble guanylate cyclase (sGC) in vascular tissues, thus elevating cellular 3',5'-cyclic guanosine monophosphate (cGMP). Because the sGC/cGMP pathway is involved in the control of platelet aggregation, we investigated whether in human platelets NaN(3) influences the responses to agonists, cGMP levels and cGMP-regulated pathways.

DESIGN AND METHOD

Concentration- and time-dependent effects of NaN(3) (1-100 micromol/L; 5-60 min incubation) on ADP- and collagen-induced aggregation, NO synthase (NOS) activity, cGMP synthesis and vasodilator-stimulated phosphoprotein (VASP) phosphorylation at Ser239 were investigated in platelets from 21 healthy individuals.

RESULTS

NaN(3) exerted concentration- and time-dependent antiaggregatory effects starting from 1 micromol/L (IC(50) with 5-min incubation: 2.77+/-0.35 micromol/L with ADP and 4.64+/-0.48 micromol/L with collagen) and significantly increased intraplatelet cGMP levels and phosphorylation of VASP at Ser239 at 1-100 micromol/L; these effects were prevented by sGC inhibition, but not by NOS inhibition.

CONCLUSIONS

NaN(3) exerts antiaggregatory effects in human platelets via activation of the sGC/cGMP/VASP pathway. This biological effect must be considered when azide-containing reagents are used for in vitro studies on platelet function.

Mechanisms of sodium azide-induced changes in intracellular calcium concentration in rat primary cortical neurons

An intracellular calcium ([Ca(2+)](i)) increase is involved in sodium azide (NaN(3))-induced neurotoxicity, an in vitro model of brain ischemia. In this study the questions of possible additional sources of calcium influx, besides glutamate receptor activation, and of the time-course of NaN(3) effects have been addressed by measuring [Ca(2+)](i) in rat primary cortical cultures with the FURA-2 method. Basal [Ca(2+)](i) of neuronal populations was concentration-dependently increased 30 min, but not 24h, after a 10-min NaN(3) (3-30 mM) treatment; conversely, the net increase induced by electrical stimulation (10Hz, 10s) was consistently reduced. All the above effects depended on glutamate release and consequent NMDA receptor activation, since the NMDA antagonist MK-801 (1 microM) prevented them, and the spontaneous efflux of [(3)H]-d-aspartate from superfused neurons was concentration-dependently increased by NaN(3). In single neuronal cells, NaN(3) application progressively and concentration-dependently increased [Ca(2+)](i) (to 177+/-5% and 249+/-7% of the controls, 4 and 12 min after a 10mM-treatment, respectively). EGTA (5mM) pretreatment reduced the effect of 10mM NaN(3) (to 118+/-5% at 4 min, and to 148+/-10% at 12 min, respectively), while 1 microM cyclosporin A did not. Both MK-801 and CNQX (a non-NMDA glutamate antagonist, 10 microM) prevented NaN(3) effect at 4 min (to 147+/-8% and 153+/-5%, respectively), but not at 12 min after NaN(3) treatment. Conversely, 10 microM verapamil and 0.1 microM omega-conotoxin (L- and N-type calcium channel blockers, respectively) significantly attenuated NaN(3) effects at 12 min (to 198+/-8% and 164+/-5%, respectively), but not at 4 min; the P/Q-type calcium channel blocker, agatoxin, 0.3 microM, was ineffective. These findings show that the predominant source of calcium increase induced by NaN(3) is extracellular, involving glutamate receptor activation in a first step and calcium channel (mainly of the N-type) opening in a second step.

How azide inhibits ATP hydrolysis by the F-ATPases

In the structure of bovine F1-ATPase determined at 1.95-A resolution with crystals grown in the presence of ADP, 5'-adenylyl-imidodiphosphate, and azide, the azide anion interacts with the beta-phosphate of ADP and with residues in the ADP-binding catalytic subunit, betaDP. It occupies a position between the catalytically essential amino acids, beta-Lys-162 in the P loop and the "arginine finger" residue, alpha-Arg-373, similar to the site occupied by the gamma-phosphate in the ATP-binding subunit, betaTP. Its presence in the betaDP-subunit tightens the binding of the side chains to the nucleotide, enhancing its affinity and thereby stabilizing the state with bound ADP. This mechanism of inhibition appears to be common to many other ATPases, including ABC transporters, SecA, and DNA topoisomerase IIalpha. It also explains the stimulatory effect of azide on ATP-sensitive potassium channels by enhancing the binding of ADP.