Regulation and pharmacological blockade of sodium-potassium ATPase: a novel pathway to neuropathy

Postpartum acute myometritis suppresses expression of contraction-associated proteins in the gravid uterus

Uterine atony is a major contributor to postpartum hemorrhage. We previously proposed the novel histological concept of postpartum acute myometritis (PAM) to elucidate the pathophysiology of uterine atony. This concept involves the infiltration of macrophages and neutrophils, as well as mast cell and complement activation in the myometrium. However, the pathological mechanism underlying uterine atony in the context of PAM remains unclear. Herein, we focused on uterine contraction-associated proteins (CAPs) including connexin 43 (Cx43), oxytocin receptors (OXR), prostaglandin receptors EP1, EP3, FP, and protease-activated receptor (PAR)-1. This follow-up study aimed to compare CAP expression between PAM and control groups. We selected 38 PAM subjects from the cases enrolled in our amniotic fluid embolism registry between 2011 and 2018. Control tissues from 10 parturients were collected during cesarean section. We stained the myometrial tissues with the following CAP markers, inflammatory cell markers, and other markers: Cx43, OXR, EP1, EP3, FP, PAR-1, C5a receptor, tryptase, neutrophil elastase, CD68, β-actin, and Na+/K+-ATPase. The immunostaining-positive areas of Cx43, OXR, EP1, EP3, and FP standardized by β-actin in the PAM tissue were significantly smaller than in the control group, whereas those of PAR-1 and Na+/K+-ATPase increased significantly in the PAM group. The Cx43- and OXR-positive areas correlated negatively with the immunostaining-positive cell numbers of CD68 and tryptase with halo, respectively. PAM may impair individual and synchronized myocyte contraction, leading to uterine atony refractory to uterotonics. Further cell-based studies are needed to elucidate the molecular mechanism by which inflammatory cells suppress CAP expression.

Terpenes in Cannabis sativa Inhibit Capsaicin Responses in Rat DRG Neurons via Na+/K+ ATPase Activation

Terpenes in Cannabis sativa exert analgesic effects, but the mechanisms are uncertain. We examined the effects of 10 terpenes on capsaicin responses in an established model of neuronal hypersensitivity. Adult rat DRG neurons cultured with neurotrophic factors NGF and GDNF were loaded with Fura2AM for calcium imaging, and treated with individual terpenes or vehicle for 5 min, followed by 1 µMol capsaicin. In vehicle treated control experiments, capsaicin elicited immediate and sustained calcium influx. Most neurons treated with terpenes responded to capsaicin after 6-8 min. Few neurons showed immediate capsaicin responses that were transient or normal. The delayed responses were found to be due to calcium released from the endoplasmic reticulum, as they were maintained in calcium/magnesium free media, but not after thapsigargin pre-treatment. Terpene inhibition of calcium influx was reversed after washout of medium, in the absence of terpenes, and in the presence of the Na+/K+ ATPase inhibitor ouabain, but not CB1 or CB2 receptor antagonists. Thus, terpenes inhibit capsaicin evoked calcium influx by Na+/K+ ATPase activation. Immunofluorescence showed TRPV1 co-expression with α1β1 Na+/K+ ATPase in most neurons while others were either TRPV1 or α1β1 Na+/K+ ATPase positive.

Effect of Cell Cycle on Cell Surface Expression of Voltage-Gated Sodium Channels and Na+,K+-ATPase

Voltage-gated sodium channels (VGSCs) are the target for many therapies. Variation in membrane potential occurs throughout the cell cycle, yet little attention has been devoted to the role of VGSCs and Na⁺,K⁺-ATPases. We hypothesized that in addition to doubling DNA and cell membrane in anticipation of cell division, there should be a doubling of VGSCs and Na⁺,K⁺-ATPase compared to non-dividing cells. We tested this hypothesis in eight immortalized cell lines by correlating immunocytofluorescent labeling of VGSCs or Na⁺,K⁺-ATPase with propidium iodide or DAPI fluorescence using flow cytometry and imaging. Cell surface expression of VGSCs during phases S through M was double that seen during phases G0–G1. By contrast, Na⁺,K⁺-ATPase expression increased only 1.5-fold. The increases were independent of baseline expression of channels or pumps. The variation in VGSC and Na⁺,K⁺-ATPase expression has implications for both our understanding of sodium’s role in controlling the cell cycle and variability of treatments targeted at these components of the Na⁺ handling system.

Targeted Osmotic Lysis: A Novel Approach to Targeted Cancer Therapies

The conventional treatment of cancer has been based on the delivery of non-selective toxins and/or ionizing energy that affect both the cancer and normal tissues in the hope of destroying the offending disease before killing the patient. Unfortunately, resistance often develops to these treatments and patients experience severe, dose-limiting adverse effects that reduce treatment efficacy and compromise quality of life. Recent advances in our knowledge of the biology of tumor cells and their microenvironment, the recognition of surface proteins that are unique to specific cancers and essential to cell growth and survival and signaling pathways associate with invasion and metastasis have led to the development of targeted therapies that are able to identify specific cellular markers and more selectively deliver lethal treatment to the invading cancer thus improving efficacy and limiting adverse effects. In the context of targeted approaches to cancer therapy, we present targeted osmotic lysis as a novel and fundamentally different approach for treating advanced-stage carcinoma that exploits the conserved relationship between voltage-gated sodium channels and Na⁺, K⁺-ATPase and has the potential to increase survival without compromising quality of life in a broad spectrum of highly malignant forms of cancer.

Emergency Use of Targeted Osmotic Lysis for the Treatment of a Patient with Aggressive Late-Stage Squamous Cell Carcinoma of the Cervix

Upregulation of voltage-gated sodium channels (VGSCs) and Na⁺/K⁺-ATPase (sodium pumps) is common across most malignant carcinomas. Targeted osmotic lysis (TOL) is a developing technology in which the concomitant stimulation of VGSCs and pharmacological blockade of sodium pumps causes rapid selective osmotic lysis of carcinoma cells. This treatment of cervical carcinoma is evidence that TOL is a safe, well-tolerated and effective treatment for aggressive advanced carcinomas that has the potential to extend life without compromising its quality. TOL is likely to have broad application for the treatment of advanced-stage carcinomas.

Targeted Osmotic Lysis of Highly Invasive Breast Carcinomas Using Pulsed Magnetic Field Stimulation of Voltage-Gated Sodium Channels and Pharmacological Blockade of Sodium Pumps

Abstract: Concurrent activation of voltage-gated sodium channels (VGSCs) and blockade of Na⁺ pumps causes a targeted osmotic lysis (TOL) of carcinomas that over-express the VGSCs. Unfortunately, electrical current bypasses tumors or tumor sections because of the variable resistance of the extracellular microenvironment. This study assesses pulsed magnetic fields (PMFs) as a potential source for activating VGSCs to initiate TOL in vitro and in vivo as PMFs are unaffected by nonconductive tissues. In vitro, PMFs (0-80 mT, 10 msec pulses, 15 pps for 10 min) combined with digoxin-lysed (500 nM) MDA-MB-231 breast cancer cells stimulus-dependently. Untreated, stimulation-only, and digoxin-only control cells did not lyse. MCF-10a normal breast cells were also unaffected. MDA-MB-231 cells did not lyse in a Na⁺-free buffer. In vivo, 30 min of PMF stimulation of MDA-MB-231 xenografts in J/Nu mice or 4T1 homografts in BALB/c mice, concurrently treated with 7 mg/kg digoxin reduced tumor size by 60-100%. Kidney, spleen, skin and muscle from these animals were unaffected. Stimulation-only and digoxin-only controls were similar to untreated tumors. BALB/C mice with 4T1 homografts survived significantly longer than mice in the three control groups. The data presented is evidence that the PMFs to activate VGSCs in TOL provide sufficient energy to lyse highly malignant cells in vitro and to reduce tumor growth of highly malignant grafts and improve host survival in vivo, thus supporting targeted osmotic lysis of cancer as a possible method for treating late-stage carcinomas without compromising noncancerous tissues.

Bromelain reversed electrolyte imbalance in the chronically constricted sciatic nerve of Wistar rats

Derangement of electrolyte in the sensory nervous system has been attributed to the development and maintenance of hyperalgesic and allodynic symptoms in painful neuropathy. This study investigated the effect of bromelain on electrolyte imbalance in chronically constricted sciatic nerve of rats (a model of neuropathic pain). Forty Wistar rats, divided into five groups of eight animals each were used for this study. von Frey filaments, tail immersion and acetone spray tests were used to assessed allodynic and thermal hyperalgesic symptoms in the Wistar rats. Sodium ion (Na⁺), potassium ion (K⁺), calcium ion (Ca²⁺) and chloride ion (Cl^-) concentrations as well as sodium-potassium and calcium electrogenic pump (Na-K ATPase and Ca ATPase, respectively) activities were estimated using spectrophotometry techniques. Bromelain significantly (p < 0.05) reversed elevation of Na⁺ and Ca²⁺ concentration compared with sciatic nerve chronic constriction injury (snCCI) group (35.68 ± 1.71 vs 44.46 ± 1.24 mg/ml/mg protein and 1.06 ± 0.19 vs 6.66 ± 0.03 mg/ml/mg protein, respectively). There were also significant (p < 0.05) increases in the level of K⁺ (0.84 ± 0.02 vs 0.36 ± 0.05 mg/ml/mg protein) and Cl^- (18.51 ± 0.29 vs 15.82 ± 0.21 mg/ml/mg protein). Bromelain reduced the activities of Ca²⁺ electrogenic pumps significantly compared with snCCI. This study therefore suggests that bromelain mitigated electrolyte imbalance in chronic constricted injury of the sciatic nerve implying that this may be an important mechanism for the anti-nociceptive effect of bromelain.

Oleandrin and Its Derivative Odoroside A, Both Cardiac Glycosides, Exhibit Anticancer Effects by Inhibiting Invasion via Suppressing the STAT-3 Signaling Pathway

The cardiac glycosides oleandrin and odoroside A, polyphenolic monomer compounds extracted from Nerium oleander, have been found to have antitumor effects on various tumors at low doses. However, the mechanisms of anticancer effects of oleandrin and odoroside A are not well known. Therefore, in this study, we aimed to investigate the anticancer effects of oleandrin and odoroside A and their associated mechanisms in highly metastatic MDA-MB-231 breast cancer cells and radiotherapy-resistant (RT-R) MDA-MB-231 cells. Our results showed that oleandrin and odoroside A dose-dependently decreased the colony formation and the invasion of both cell lines at nanomolar ranges. Furthermore, oleandrin (50 nM) and odoroside A (100 nM) reduced octamer-binding transcription factor 3/4 (OCT3/4) and β-catenin levels and matrix metalloproteinase-9 (MMP-9) activity. Finally, we found that phospho-STAT-3 levels were increased in MDA-MB-231 and RT-R-MDA-MB-231, but not in endothelial cells (ECs), and that the levels were significantly decreased by oleandrin (50 nM) and odoroside A (100 nM). Inhibition of phospho-signal transducer and activator of transcription (STAT)-3 significantly reduced OCT3/4 and β-catenin levels and MMP-9 activity, ultimately resulting in reduced invasion. These results suggest that the anticancer effects of oleandrin and odoroside A might be due to the inhibition of invasion through of phospho-STAT-3-mediated pathways that are involved in the regulation of invasion-related molecules.

Selective lysis of breast carcinomas by simultaneous stimulation of sodium channels and blockade of sodium pumps

Sodium influx through voltage-gated sodium channels (VGSCs) coupled with balanced removal of sodium ions via Na⁺, K⁺-ATPase is a major determinant of cellular homeostasis and intracellular ionic concentration. Interestingly, many metastatic carcinomas express high levels of these channels. We hypothesized that if excess VGSCs are activated and Na⁺, K⁺-ATPase is simultaneously blocked, the intracellular Na⁺ concentration should increase, resulting in water movement into the cell, causing swelling and lytic cell death. MDA-MB-231 breast cancer cells over-express VGSCs by 7-fold. To test our hypothesis, we treated these cells in vitro with the Na⁺, K⁺-ATPase blocker, ouabain, and then stimulated with a sublethal electric current. For in vivo histologic and survival studies, MDA-MB-231 xenografts were established in Nu/J mice. Mice injected with saline or ouabain were electrically stimulated with trains of 10 msec 10V DC pulses. Within seconds to minutes, the cells swelled and lysed. MCF-10a cells, which express normal VGSCs levels, were unaffected by this treatment. Cells from the weakly-malignant cell line, MCF-7, which express 3-fold greater VGSCs than MCF-10a cells, displayed an intermediate time-to-lysis. The rate of lysis correlated directly with the degree of sodium channel expression and malignancy. We also demonstrated efficacy in cell lines from prostate, colon and lung carcinomas. Treated MDA-MB-231 xenografts showed 60-80% cell death. In survival studies, TOL-treated mice showed significantly slower tumor growth vs. controls. These results are evidence that this "targeted osmotic lysis" represents a novel method for selectively killing cancer cells and warrants further investigation as a potential treatment for advanced and end-stage breast cancer.

Epi-reevesioside F inhibits Na+/K+-ATPase, causing cytosolic acidification, Bak activation and apoptosis in glioblastoma

Epi-reevesioside F, a new cardiac glycoside isolated from the root of Reevesia formosana, displayed potent activity against glioblastoma cells. Epi-reevesioside F was more potent than ouabain with IC₅₀ values of 27.3±1.7 vs. 48.7±1.8 nM (P < 0.001) and 45.0±3.4 vs. 81.3±4.3 nM (P < 0.001) in glioblastoma T98 and U87 cells, respectively. However, both Epi-reevesioside F and ouabain were ineffective in A172 cells, a glioblastoma cell line with low Na⁺/K⁺-ATPase α3 subunit expression. Epi-reevesioside F induced cell cycle arrest at S and G2 phases and apoptosis. It also induced an increase of intracellular concentration of Na⁺ but not Ca²⁺, cleavage and exposure of N-terminus of Bak, loss of mitochondrial membrane potential, inhibition of Akt activity and induction of caspase cascades. Potassium supplements significantly inhibited Epi-reevesioside F-induced effects. Notably, Epi-reevesioside F caused cytosolic acidification that was highly correlated with the anti-proliferative activity. In summary, the data suggest that Epi-reevesioside F inhibits Na⁺/K⁺-ATPase, leading to overload of intracellular Na⁺ and cytosolic acidification, Bak activation and loss of mitochondrial membrane potential. The PI3-kinase/Akt pathway is inhibited and caspase-dependent apoptosis is ultimately triggered in Epi-reevesioside F-treated glioblastoma cells.

Proteasome Inhibition Contributed to the Cytotoxicity of Arenobufagin after Its Binding with Na, K-ATPase in Human Cervical Carcinoma HeLa Cells

Although the possibility of developing cardiac steroids/cardiac glycosides as novel cancer therapeutic agents has been recognized, the mechanism of their anticancer activity is still not clear enough. Toad venom extract containing bufadienolides, which belong to cardiac steroids, has actually long been used as traditional Chinese medicine in clinic for cancer therapy in China. The cytotoxicity of arenobufagin, a bufadienolide isolated from toad venom, on human cervical carcinoma HeLa cells was checked. And, the protein expression profile of control HeLa cells and HeLa cells treated with arenobufagin for 48 h was analyzed using two-dimensional electrophoresis, respectively. Differently expressed proteins in HeLa cells treated with arenobufagin were identified and the pathways related to these proteins were mapped from KEGG database. Computational molecular docking was performed to verify the binding of arenobufagin and Na, K-ATPase. The effects of arenobufagin on Na, K-ATPase activity and proteasome activity of HeLa cells were checked. The protein-protein interaction network between Na, K-ATPase and proteasome was constructed and the expression of possible intermediate proteins ataxin-1 and translationally-controlled tumor protein in HeLa cells treated with arenobufagin was then checked. Arenobufagin induced apoptosis and G2/M cell cycle arrest in HeLa cells. The cytotoxic effect of arenobufagin was associated with 25 differently expressed proteins including proteasome-related proteins, calcium ion binding-related proteins, oxidative stress-related proteins, metabolism-related enzymes and others. The results of computational molecular docking revealed that arenobufagin was bound in the cavity formed by the transmembrane alpha subunits of Na, K-ATPase, which blocked the pathway of extracellular Na⁺/K⁺ cation exchange and inhibited the function of ion exchange. Arenobufagin inhibited the activity of Na, K-ATPase and proteasome, decreased the expression of Na, K-ATPase α1 and α3 subunits and increased the expression of WEE1 in HeLa cells. Antibodies against Na, K-ATPase α1 and α3 subunits alone or combinated with arenobufagin also inhibited the activity of proteasome. Furthermore, the expression of the possible intermediate proteins ataxin-1 and translationally-controlled tumor protein was increased in HeLa cells treated with arenobufagin by flow cytometry analysis, respectively. These results indicated that arenobufagin might directly bind with Na, K-ATPase α1 and α3 subunits and the inhibitive effect of arenobufagin on proteasomal activity of HeLa cells might be related to its binding with Na, K-ATPase.

Cardiotonic Steroids as Modulators of Neuroinflammation

Cardiotonic steroids (CTS) are a class of specific ligands of the Na(+), K(+)- ATPase (NKA). NKA is a P-type ATPase that is ubiquitously expressed and although well known to be responsible for the maintenance of the cell electrochemical gradient through active transport, NKA can also act as a signal transducer in the presence of CTS. Inflammation, in addition to importantly driving organism defense and survival mechanisms, can also modulate NKA activity and memory formation, as well as being relevant to many chronic illnesses, neurodegenerative diseases, and mood disorders. The aim of the current review is to highlight the recent advances as to the role of CTS and NKA in inflammatory process, with a particular focus in the central nervous system.