Update on a brain-penetrant cardiac glycoside that can lower cellular prion protein levels in human and guinea pig paradigms.

Lowering the levels of the cellular prion protein (PrPC) is widely considered a promising strategy for the treatment of prion diseases. Building on work that established immediate spatial proximity of PrPC and Na+, K+-ATPases (NKAs) in the brain, we recently showed that PrPC levels can be reduced by targeting NKAs with their natural cardiac glycoside (CG) inhibitors. We then introduced C4'-dehydro-oleandrin as a CG with improved pharmacological properties for this indication, showing that it reduced PrPC levels by 84% in immortalized human cells that had been differentiated to acquire neural or astrocytic characteristics. Here we report that our lead compound caused cell surface PrPC levels to drop also in other human cell models, even when the analyses of whole cell lysates suggested otherwise. Because mice are refractory to CGs, we explored guinea pigs as an alternative rodent model for the preclinical evaluation of C4'-dehydro-oleandrin. We found that guinea pig cell lines, primary cells, and brain slices were responsive to our lead compound, albeit it at 30-fold higher concentrations than human cells. Of potential significance for other PrPC lowering approaches, we observed that cells attempted to compensate for the loss of cell surface PrPC levels by increasing the expression of the prion gene, requiring daily administration of C4'-dehydro-oleandrin for a sustained PrPC lowering effect. Regrettably, when administered systemically in vivo, the levels of C4'-dehydro-oleandrin that reached the guinea pig brain remained insufficient for the PrPC lowering effect to manifest. A more suitable preclinical model is still needed to determine if C4'-dehydro-oleandrin can offer a cost-effective complementary strategy for pushing PrPC levels below a threshold required for long-term prion disease survival.

Vascular smooth muscle BK channels limit ouabain-induced vasocontraction: Dual role of the Na/K-ATPase as a hub for Src-kinase and the Na/Ca-exchanger.

Large-conductance, calcium-activated potassium channels (BK channels) and the Na/K-ATPase are expressed universally in vascular smooth muscle. The Na/K-ATPase may act via changes in the intracellular Ca2+ concentration mediated by the Na/Ca exchanger (NCX) and via Src kinase. Both pathways are known to regulate BK channels. Whether BK channels functionally interact in vascular smooth muscle cells with the Na/K-ATPase remains to be elucidated. Thus, this study addressed the hypothesis that BK channels limit ouabain-induced vasocontraction. Rat mesenteric arteries were studied using isometric myography, FURA-2 fluorimetry and proximity ligation assay. The BK channel blocker iberiotoxin potentiated methoxamine-induced contractions. The cardiotonic steroid, ouabain (10-5 M), induced a contractile effect of IBTX at basal tension prior to methoxamine administration and enhanced the pro-contractile effect of IBTX on methoxamine-induced contractions. These facilitating effects of ouabain were prevented by the inhibition of either NCX or Src kinase. Furthermore, inhibition of NCX or Src kinase reduced the BK channel-mediated negative feedback regulation of arterial contraction. The effects of NCX and Src kinase inhibition were independent of each other. Co-localization of the Na/K-ATPase and the BK channel was evident. Our data suggest that BK channels limit ouabain-induced vasocontraction by a dual mechanism involving the NCX and Src kinase signaling. The data propose that the NCX and the Src kinase pathways, mediating the ouabain-induced activation of the BK channel, act in an independent manner.

The natural compound periplogenin suppresses the growth of prostate carcinoma cells by directly targeting ATP1A1.

Natural compounds constitute a major resource for the development of medicines for multiple diseases. While many natural compounds show strong biological activity, the mechanisms that confer clinical benefits are often elusive and have been attributed to multiple pathways. Periplogenin (PPG), a natural compound isolated from Cortex periplocae, exhibits strong anti-tumor activities in several human cancer cell lines. However, its molecular mode of action remained unclear. In this study, we leveraged a forward genetic screening approach in DU145 prostate cancer cells to uncover the molecular target of PPG using chemical mutagenesis. Next generation sequencing revealed that a single amino acid substitution at amino acid 804 in ATP1A1 (ATPase Na + /K + Transporting Subunit Alpha 1) confers resistance to the cytotoxic activity of PPG. Mechanistically, ATP1A1 T804 forms a hydrogen bond with PPG which is abolished by the T804A substitution in ATP1A1, resulting in resistance to PPG treatment in vitro. Importantly, in vivo, PPG strongly suppressed tumor development in a DU145 xenograft model whereas DU145 xenograft tumors carrying a ATP1A1-T804A mutation were largely unaffected by the treatment. These findings demonstrate that PPG suppresses the growth of DU145 prostate cancer cells in vitro and in vivo by directly binding to ATP1A1 and highlight the power of our unbiased forward genetic screening approach to uncover direct drug target structures at single amino acid resolution.

Influence of Anticholinesterase Drugs on Activity and Properties of Na+,K+-ATPase in Rat Erythrocytes under Stress Caused by Intense Physical Exercise.

We studied the effect of intramuscular injection of physostigmine and neostigmine on Na+,K+-ATPase activity in erythrocytes of rats subjected to intense physical exercise. Both anticholinesterase drugs had a significant effect on the development of the stress response, which was expressed in a decrease in the manifestation of its individual components such as the concentration of ascorbic acid in the adrenal glands, stress-related erythrocyte polycythemia, and LPO indicators. Anticholinesterase drugs reverse the stress-induced decrease in Na+,K+-ATPase activity, as well as changes in its magnesium-dependent properties. There were no changes in the activity of the studied enzyme in the erythrocyte ghosts. We associate the observed differences with the correction of the functions of the cholinergic components of the hypothalamic-pituitary-adrenal axis leading to the development of a hypoergic type stress reaction.

Hepatocyte Growth Factor Modulates Corneal Endothelial Wound Healing In Vitro.

In this study, we assessed the impact of hepatocyte growth factor (HGF) on corneal endothelial cells (CECs), finding that HGF concentrations of 100-250 ng/mL significantly increased CEC proliferation by 30%, migration by 32% and improved survival under oxidative stress by 28% compared to untreated controls (p < 0.05). The primary objective was to identify non-fibrotic pharmacological strategies to enhance corneal endothelial regeneration, addressing a critical need in conditions like Fuchs' endothelial dystrophy (FED), where donor tissue is scarce. To confirm the endothelial nature of the cultured CECs, Na+/K+-ATPase immunohistochemistry was performed. Proliferation rates were determined through BrdU incorporation assays, while cell migration was assessed via scratch assays. Cell viability was evaluated under normal and oxidative stress conditions using WST-1 assays. To ensure that HGF treatment did not trigger epithelial-mesenchymal transition, which could lead to undesirable fibrotic changes, α-SMA staining was conducted. These comprehensive methodologies provided robust data on the effects of HGF, confirming its potential as a therapeutic agent for corneal endothelial repair without inducing harmful EMT, as indicated by the absence of α-SMA expression. These findings suggest that HGF holds therapeutic promise for enhancing corneal endothelial repair, warranting further investigation in in vivo models to confirm its clinical applicability.

Influence of Intraocular Pressure on the Expression and Activity of Sodium-Potassium Pumps in the Corneal Endothelium.

The corneal endothelium is responsible for pumping fluid out of the stroma in order to maintain corneal transparency, which depends in part on the expression and activity of sodium-potassium pumps. In this study, we evaluated how physiologic pressure and flow influence transcription, protein expression, and activity of Na+/K+-ATPase. Native and engineered corneal endothelia were cultured in a bioreactor in the presence of pressure and flow (hydrodynamic culture condition) or in a Petri dish (static culture condition). Transcription of ATP1A1 was assessed using qPCR, the expression of the α1 subunit of Na+/K+-ATPase was measured using Western blots and ELISA assays, and Na+/K+-ATPase activity was evaluated using an ATPase assay in the presence of ouabain. Results show that physiologic pressure and flow increase the transcription and the protein expression of Na+/K+-ATPase α1 in engineered corneal endothelia, while they remain stable in native corneal endothelia. Interestingly, the activity of Na+/K+-ATPase was increased in the presence of physiologic pressure and flow in both native and engineered corneal endothelia. These findings highlight the role of the in vivo environment on the functionality of the corneal endothelium.

The Na+/K+-ATPase generically enables deterministic bursting in class I neurons by shearing the spike-onset bifurcation structure.

Slow brain rhythms, for example during slow-wave sleep or pathological conditions like seizures and spreading depolarization, can be accompanied by oscillations in extracellular potassium concentration. Such slow brain rhythms typically have a lower frequency than tonic action-potential firing. They are assumed to arise from network-level mechanisms, involving synaptic interactions and delays, or from intrinsically bursting neurons. Neuronal burst generation is commonly attributed to ion channels with slow kinetics. Here, we explore an alternative mechanism generically available to all neurons with class I excitability. It is based on the interplay of fast-spiking voltage dynamics with a one-dimensional slow dynamics of the extracellular potassium concentration, mediated by the activity of the Na+/K+-ATPase. We use bifurcation analysis of the complete system as well as the slow-fast method to reveal that this coupling suffices to generate a hysteresis loop organized around a bistable region that emerges from a saddle-node loop bifurcation-a common feature of class I excitable neurons. Depending on the strength of the Na+/K+-ATPase, bursts are generated from pump-induced shearing the bifurcation structure, spiking is tonic, or cells are silenced via depolarization block. We suggest that transitions between these dynamics can result from disturbances in extracellular potassium regulation, such as glial malfunction or hypoxia affecting the Na+/K+-ATPase activity. The identified minimal mechanistic model outlining the sodium-potassium pump's generic contribution to burst dynamics can, therefore, contribute to a better mechanistic understanding of pathologies such as epilepsy syndromes and, potentially, inform therapeutic strategies.

Phenotype Distinctions in Mice Deficient in the Neuron-Specific α3 Subunit of Na,K-ATPase: Atp1a3tm1Ling/+ and Atp1a3 +/D801Y.

ATP1A3 is a Na,K-ATPase gene expressed specifically in neurons in the brain. Human mutations are dominant and produce an unusually wide spectrum of neurological phenotypes, most notably rapid-onset dystonia parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). Here we compared heterozygotes of two mouse lines, a line with little or no expression (Atp1a3tm1Ling/+) and a knock-in expressing p.Asp801Tyr (D801Y, Atp1a3 +/D801Y). Both mouse lines had normal lifespans, but Atp1a3 +/D801Y had mild perinatal mortality contrasting with D801N mice (Atp1a3 +/D801N), which had high mortality. The phenotypes of Atp1a3tm1Ling/+ and Atp1a3 +/D801Y were different, and testing of each strain was tailored to its symptom range. Atp1a3tm1Ling/+ mice displayed little at baseline, but repeated ethanol intoxication produced hyperkinetic motor abnormalities not seen in littermate controls. Atp1a3 +/D801Y mice displayed robust phenotypes: hyperactivity, diminished posture consistent with hypotonia, and deficiencies in beam walk and wire hang tests. Symptoms also included qualitative motor abnormalities that are not well quantified by conventional tests. Paradoxically, Atp1a3 +/D801Y showed sustained better performance than wild type on the accelerating rotarod. Atp1a3 +/D801Y mice were overactive in forced swimming and afterward had intense shivering, transient dystonic postures, and delayed recovery. Remarkably, Atp1a3 +/D801Y mice were refractory to ketamine anesthesia, which elicited hyperactivity and dyskinesia even at higher dose. Neither mouse line exhibited fixed dystonia (typical of RDP patients), spontaneous paroxysmal weakness (typical of AHC patients), or seizures but had consistent, measurable neurological abnormalities. A gradient of variation supports the importance of studying multiple Atp1a3 mutations in animal models to understand the roles of this gene in human disease.

Gill ionocyte remodeling mediates blood pH regulation in rockfish (Sebastes diploproa) exposed to environmentally relevant hypercapnia.

Marine fishes excrete excess H+ using basolateral Na+-K+-ATPase (NKA) and apical Na+/H+ exchanger 3 (NHE3) in gill ionocytes. However, the mechanisms that regulate H+ excretion during exposure to environmentally relevant hypercapnia (ERH) remain poorly understood. Here, we explored transcriptomic, proteomic, and cellular responses in gills of juvenile splitnose rockfish (Sebastes diploproa) exposed to 3 days of ERH conditions (pH ∼7.5, ∼1,600 µatm Pco2). Blood pH was fully regulated at ∼7.75 despite a lack of significant changes in gill 1) mRNAs coding for proteins involved in blood acid-base regulation, 2) total NKA and NHE3 protein abundance, and 3) ionocyte density. However, ERH-exposed rockfish demonstrated increased NKA and NHE3 abundance on the ionocyte plasma membrane coupled with wider apical membranes and greater extension of apical microvilli. The observed gill ionocyte remodeling is consistent with enhanced H+ excretion that maintains blood pH homeostasis during exposure to ERH and does not necessitate changes at the expression or translation levels. These mechanisms of phenotypic plasticity may allow fishes to regulate blood pH during environmentally relevant acid-base challenges and thus have important implications for both understanding how organisms respond to climate change and for selecting appropriate metrics to evaluate its impact on marine ecosystems.NEW & NOTEWORTHY Splitnose rockfish exposed to environmentally relevant hypercapnia utilize existing proteins (rather than generate additional machinery) to maintain homeostasis.

Sodium chloride in the tumor microenvironment enhances T cell metabolic fitness and cytotoxicity.

The efficacy of antitumor immunity is associated with the metabolic state of cytotoxic T cells, which is sensitive to the tumor microenvironment. Whether ionic signals affect adaptive antitumor immune responses is unclear. In the present study, we show that there is an enrichment of sodium in solid tumors from patients with breast cancer. Sodium chloride (NaCl) enhances the activation state and effector functions of human CD8+ T cells, which is associated with enhanced metabolic fitness. These NaCl-induced effects translate into increased tumor cell killing in vitro and in vivo. Mechanistically, NaCl-induced changes in CD8+ T cells are linked to sodium-induced upregulation of Na+/K+-ATPase activity, followed by membrane hyperpolarization, which magnifies the electromotive force for T cell receptor (TCR)-induced calcium influx and downstream TCR signaling. We therefore propose that NaCl is a positive regulator of acute antitumor immunity that might be modulated for ex vivo conditioning of therapeutic T cells, such as CAR T cells.

COMPARATIVE ANALYSIS OF MEMORY AND BEHAVIORAL CHANGES AFTER RADON-CONTAINED MINERAL WATER INHALATION THERAPY IN AGED RATS.

This research article elucidates the pivotal role of radiopharmacy in the contemporary landscape, underscoring its potential therapeutic efficacy in addressing symptoms associated with aged-related neurocognitive processes. Clinical trials, characterized by the judicious application of modest radiation doses, exemplified by low-dose radon, have yielded affirmative outcomes in the amelioration of aged, related symptoms. MATERIAL AND METHODS: The study was conducted on an animal model. The effect of low doses of radon on cognitive processes is being studied by inhalation of randomized mineral water. Changes in the clinical picture were studied using behavioral tests, namely the Barnes maze tests. At the cellular level, radon-contained water inhalation causes different changes: in the fraction of synaptic membranes (determined by Na, K-ATPase activity), aged, related changes by telomerase activity and oxidative stress level changes. RESULTS: Our studies show that age-related changes in brain tissue are less noticeable after radon inhalation, namely, the concentration of amyloid plaques decreases in a group of aged rats after radon therapy. A significant improvement in cognitive function was observed after radon inhalation in aged rats. CONCLUSION: The results show that exposure to radon-containing mineral water leads to improved spatial perception, potentially improving age-related cognitive functions not only at the level of neurocognitive tests, but also changes at the level of cellular functioning.

Biophysical Analysis of a Minimalistic Kidney Model Expressing SGLT1 Reveals Crosstalk between Luminal and Lateral Membranes and a Plausible Mechanism of Isosmotic Transport.

We extended our model of the S1 tubular segment to address the mechanisms by which SGLT1 interacts with lateral Na/K pumps and tight junctional complexes to generate isosmotic fluid reabsorption via tubular segment S3. The strategy applied allowed for simulation of laboratory experiments. Reproducing known experimental results constrained the range of acceptable model outputs and contributed to minimizing the free parameter space. (1) In experimental conditions, published Na and K concentrations of proximal kidney cells were found to deviate substantially from their normal physiological levels. Analysis of the mechanisms involved suggested insufficient oxygen supply as the cause and, indirectly, that a main function of the Na/H exchanger (NHE3) is to extrude protons stemming from mitochondrial energy metabolism. (2) The water path from the lumen to the peritubular space passed through aquaporins on the cell membrane and claudin-2 at paracellular tight junctions, with an additional contribution to water transport by the coupling of 1 glucose:2 Na:400 H2O in SGLT1. (3) A Na-uptake component passed through paracellular junctions via solvent drag in Na- and water-permeable claudin-2, thus bypassing the Na/K pump, in agreement with the findings of early studies. (4) Electrical crosstalk between apical rheogenic SGLT1 and lateral rheogenic Na/K pumps resulted in tight coupling of luminal glucose uptake and transepithelial water flow. (5) Isosmotic transport was achieved by Na-mediated ion recirculation at the peritubular membrane.

Uncovering key steps in FGF12 cellular release reveals a common mechanism for unconventional FGF protein secretion.

FGF12 belongs to a subfamily of FGF proteins called FGF homologous factors (FHFs), which until recently were thought to be non-signaling intracellular proteins. Our recent studies have shown that although they lack a conventional signal peptide for secretion, they can reach the extracellular space, especially under stress conditions. Here, we unraveled that the long "a" isoform of FGF12 is secreted in a pathway involving the A1 subunit of Na(+)/K(+) ATPase (ATP1A1), Tec kinase and lipids such as phosphatidylinositol and phosphatidylserine. Further, we showed that the short "b" isoform of FGF12, which binds ATP1A1 and phosphatidylserine less efficiently, is not secreted from cells. We also indicated regions in the FGF12a protein sequence that are crucial for its secretion, including N-terminal fragment and specific residues, and proposed that liquid-liquid phase separation may be important in this process. Our results strongly suggest that the mechanism of this process is very similar for all unconventionally secreted FGF proteins.

Sex-dependent changes in AMPAR expression and Na, K-ATPase activity in the cerebellum and hippocampus of α-Klotho-Hypomorphic mice.

Aging is characterized by a functional decline in several physiological systems. α-Klotho-hypomorphic mice (Kl-/-) exhibit accelerated aging and cognitive decline. We evaluated whether male and female α-Klotho-hypomorphic mice show changes in the expression of synaptic proteins, N-methyl-d-aspartate receptor (NMDAR) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits, postsynaptic density protein 95 (PSD-95), synaptophysin and synapsin, and the activity of Na+, K+-ATPase (NaK) isoforms in the cerebellum and hippocampus. In this study, we demonstrated that in the cerebellum, Kl-/- male mice have reduced expression of GluA1 (AMPA) compared to wild-type (Kl+/+) males and Kl-/- females. Also, Kl-/- male and female mice show reduced ɑ2/ɑ3-NaK and Mg2+-ATPase activities in the cerebellum, respectively, and sex-based differences in NaK and Mg2+-ATPase activities in both the regions. Our findings suggest that α-Klotho could influence the expression of AMPAR and the activity of NaK isoforms in the cerebellum in a sex-dependent manner, and these changes may contribute, in part, to cognitive decline.

Establishment of a transgene-free iPS cell line (SDCHi007-A) from a young patient bearing a ATP1A2 mutation and suffering from Epilepsy.

Epilepsy is a chronic neurological disease. Here we describe the generation of induced pluripotent stem cells (iPSCs) from a patient diagnosed as epilepsy caused by ATP1A2 gene mutation. Induced pluripotent stem cells (iPSCs) were developed using non-integrating episomal vectors containing OCT4, SOX2, KLF4, BCL-XL and C-MYC. The established iPSC line (SDCHi007-A) displayed pluripotent cell morphology, high expression levels of pluripotency markers, differentiation potential in vitro, normal karyotype, and remaining the original ATP1A2 gene mutation.

Impact of RAAS Receptors and Membrane-Bound Transporter System in the Left Ventricle during the Long-Term Control of Hypertension.

The Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in systemic and neurogenic hypertension. The infusion of RAAS inhibitors blunted arterial pressure and efficacy of use-dependent synaptic transmission in sympathetic ganglia. The current investigation aims to elucidate the impact of RAAS-mediated receptors on left ventricular cardiomyocytes and the role of the sarcolemma-bound carrier system in the heart of the hypertensive transgene model. A significant increase in mRNA and the protein expression for angiotensin II (AngII) receptor subtype-1 (AT1R) was observed in (mREN2)27 transgenic compared to the normotensive rodents. Concurrently, there was an upregulation in AT1R and a downregulation in the MAS1 proto-oncogene protein receptor as well as the AngII subtype-2 receptor in hypertensive rodents. There were modifications in the expressions of sarcolemma Na+-K+-ATPase, Na+-Ca2+ exchanger, and Sarcoendoplasmic Reticulum Calcium ATPase in the transgenic hypertensive model. These observations suggest chronic RAAS activation led to a shift in receptor balance favoring augmented cardiac contractility and disruption in calcium handling through modifications of membrane-bound carrier proteins and blood pressure. The study provides insight into mechanisms underlying RAAS-mediated cardiac dysfunction and highlights the potential value of targeting the protective arm of AngII in hypertension.

Alterations of Placental Sodium in Preeclampsia: Trophoblast Responses.

BACKGROUND: Evidence suggests that increasing salt intake in pregnancy lowers blood pressure, protecting against preeclampsia. We hypothesized that sodium (Na+) evokes beneficial placental signals that are disrupted in preeclampsia. METHODS: Blood and urine were collected from nonpregnant women of reproductive age (n=26) and pregnant women with (n=50) and without (n=55) preeclampsia, along with placental biopsies. Human trophoblast cell lines and primary human trophoblasts were cultured with varying Na+ concentrations. RESULTS: Women with preeclampsia had reduced placental and urinary Na+ concentrations, yet increased urinary angiotensinogen and reduced active renin, aldosterone concentrations, and osmotic response signal TonEBP (tonicity-responsive enhancer binding protein) expression. In trophoblast cell cultures, TonEBP was consistently increased upon augmented Na+ exposure. Mechanistically, inhibiting Na+/K+-ATPase or adding mannitol evoked the TonEBP response, whereas inhibition of cytoskeletal signaling abolished it. CONCLUSIONS: Enhanced Na+ availability induced osmotic gradient-dependent cytoskeletal signals in trophoblasts, resulting in proangiogenic responses. As placental salt availability is compromised in preeclampsia, adverse systemic responses are thus conceivable.

Na,K-ATPase Expression Can Be Limited Post-Transcriptionally: A Test of the Role of the Beta Subunit, and a Review of Evidence.

The Na,K-ATPase is an α-ß heterodimer. It is well known that the Na,K-ATPase ß subunit is required for the biosynthesis and trafficking of the α subunit to the plasma membrane. During investigation of properties of human ATP1A3 mutations in 293 cells, we observed a reciprocal loss of endogenous ATP1A1 when expressing ATP1A3. Scattered reports going back as far as 1991 have shown that experimental expression of one subunit can result in reduction in another, suggesting that the total amount is strictly limited. It seems logical that either α or ß subunit should be rate-limiting for assembly and functional expression. Here, we present evidence that neither α nor ß may be limiting and that there is another level of control that limits the amount of Na,K-ATPase to physiological levels. We propose that α subunits compete for something specific, like a private chaperone, required to finalize their biosynthesis or to prevent their degradation in the endoplasmic reticulum.

Water-accommodated fractions of crude oil and its mixture with chemical dispersant impairs oxidase stress and energy metabolism disorders in Oryzias melastigma embryos.

In this study, marine medaka (Oryzias melastigma) embryos were exposed to different concentrations of water-accommodated fractions (WAFs) and chemically enhanced water-accommodated fractions (CEWAFs) of Oman crude oil for 14 d by semi-static exposure methods. The effects on growth and development and energy metabolism process were evaluated. Results showed that embryo survival and hatchability were decreased in a dose-dependent manner with an increase in the concentration of petroleum hydrocarbon compounds, whereas the malformation exhibited a dose-dependent increase. Compared to the control, the adenosine triphosphate (ATP) content and Na+-K+-ATPase (NKA) activities of embryos exposed to both WAFs and CEWAFs were reduced, while intracellular reactive oxygen species (ROS) levels and NADH oxidase (NOX) activities were increased. Our study demonstrated that exposure to crude oil dispersed by chemical dispersant affected the growth and development of marine medaka embryos, caused oxidative stress while produced a series of malformations in the body and dysregulation in energy metabolism. In comparison, the toxic effects of chemically dispersed crude oil might be more severe than the oil itself in the equivalent diluted concentration treatment solution. These would provide more valuable and reliable reference data for the use of chemical dispersants in oil spills.

[Effects of PM2.5 and O3 sub-chronic combined exposure on ATP amount and ATPase activities in rat nasal mucosa].

OBJECTIVE: To evaluate the effects of fine particle matter (PM2.5) and ozone (O3) combined exposure on adenosine triphosphate (ATP) amount and ATPase activities in nasal mucosa of Sprague Dawley (SD) rats. METHODS: Twenty male SD rats were divided into control group (n=10) and exposure group (n=10) by random number table method. The rats were fed in the conventional clean environment and the air pollutant exposure system established by our team, respectively, and exposed for 208 d. During the exposure period, the concentrations of PM2.5 and O3 in the exposure system were monitored, and a comprehensive assessment of PM2.5 and O3 in the exposure system was conducted by combining self-measurement and site data. On the 208 d of exposure, the core, liver, spleen, kidney, testis and other major organs and nasal mucosal tissues of the rats were harvested. Each organ was weighed and the organ coefficient calculated. The total amount of ATP was measured by bioluminescence, and the activities of Na+-K+ -ATPase and Ca2+ -ATPase were detected by spectrophotometry. The t test of two independent samples was used to compare the differences among the indicator groups. RESULTS: From the 3rd week to the end of exposure duration, the body weight of the rats in the exposure group was higher than that in the control group (P < 0.05), and there was no significant difference in organ coefficients between the two groups. The average daily PM2.5 concentration in the exposure group was (30.68±19.23) µg/m3, and the maximum 8 h ozone concentration (O3-8 h) was (82.45±35.81) µg/m3. The chemiluminescence value (792.4±274.1) IU/L of ATP in nasal mucosa of the rats in the exposure group was lower than that in the control group (1 126.8±218.1) IU/L. The Na+-K+-ATPase activity (1.53±0.85) U/mg in nasal mucosa of the rats in the exposure group was lower than that in the control group (4.31±1.60) U/mg (P < 0.05). The protein content of nasal mucosa in the control group and the exposure group were (302.14±52.51) mg/L and (234.58±53.49) mg/L, respectively, and the activity of Ca2+-ATPase was (0.81±0.27) U/mg and (0.99±0.73) U/mg, respectively. There was no significant difference between the groups. CONCLUSION: The ability of power capacity decreased in the rat nasal mucossa under the sub-chronic low-concentration exposure of PM2.5 and O3.