Regulation of Na+, K+-ATPase by the endogenous sodium transport inhibitor from hypothalamus

Differential whole-genome doubling based signatures for improvement on clinical outcomes and drug response in patients with breast cancer

Whole genome doublings (WGD), a hallmark of human cancer, is pervasive in breast cancer patients. However, the molecular mechanism of the complete impact of WGD on survival and treatment response in breast cancer remains unclear. To address this, we performed a comprehensive and systematic analysis of WGD, aiming to identify distinct genetic alterations linked to WGD and highlight its improvement on clinical outcomes and treatment response for breast cancer. A linear regression model along with weighted gene co-expression network analysis (WGCNA) was applied on The Cancer Genome Atlas (TCGA) dataset to identify critical genes related to WGD. Further Cox regression models with random selection were used to optimize the most useful prognostic markers in the TCGA dataset. The clinical implication of the risk model was further assessed through prognostic impact evaluation, tumor stratification, functional analysis, genomic feature difference analysis, drug response analysis, and multiple independent datasets for validation. Our findings revealed a high aneuploidy burden, chromosomal instability (CIN), copy number variation (CNV), and mutation burden in breast tumors exhibiting WGD events. Moreover, 247 key genes associated with WGD were identified from the distinct genomic patterns in the TCGA dataset. A risk model consisting of 22 genes was optimized from the key genes. High-risk breast cancer patients were more prone to WGD and exhibited greater genomic diversity compared to low-risk patients. Some oncogenic signaling pathways were enriched in the high-risk group, while primary immune deficiency pathways were enriched in the low-risk group. We also identified a risk gene, ANLN (anillin), which displayed a strong positive correlation with two crucial WGD genes, KIF18A and CCNE2. Tumors with high expression of ANLN were more prone to WGD events and displayed worse clinical survival outcomes. Furthermore, the expression levels of these risk genes were significantly associated with the sensitivities of BRCA cell lines to multiple drugs, providing valuable insights for targeted therapies. These findings will be helpful for further improvement on clinical outcomes and contribution to drug development in breast cancer.

On the Many Actions of Ouabain: Pro-Cystogenic Effects in Autosomal Dominant Polycystic Kidney Disease

Ouabain and other cardenolides are steroidal compounds originally discovered in plants. Cardenolides were first used as poisons, but after finding their beneficial cardiotonic effects, they were rapidly included in the medical pharmacopeia. The use of cardenolides to treat congestive heart failure remained empirical for centuries and only relatively recently, their mechanisms of action became better understood. A breakthrough came with the discovery that ouabain and other cardenolides exist as endogenous compounds that circulate in the bloodstream of mammals. This elevated these compounds to the category of hormones and opened new lines of investigation directed to further study their biological role. Another important discovery was the finding that the effect of ouabain was mediated not only by inhibition of the activity of the Na,K-ATPase (NKA), but by the unexpected role of NKA as a receptor and a signal transducer, which activates a complex cascade of intracellular second messengers in the cell. This broadened the interest for ouabain and showed that it exerts actions that go beyond its cardiotonic effect. It is now clear that ouabain regulates multiple cell functions, including cell proliferation and hypertrophy, apoptosis, cell adhesion, cell migration, and cell metabolism in a cell and tissue type specific manner. This review article focuses on the cardenolide ouabain and discusses its various in vitro and in vivo effects, its role as an endogenous compound, its mechanisms of action, and its potential use as a therapeutic agent; placing especial emphasis on our findings of ouabain as a pro-cystogenic agent in autosomal dominant polycystic kidney disease (ADPKD).

Modulatory effect of some steroid hormones, their glucuronides and ouabain-like compounds on Cavia cobaya kidney Na+,K(+)-ATPase activity

1. Ouabain-like compounds (approx. mol. wt 700, 2,000 and 4,000 Da) were purified from plasma of essential hypertensive patients. 2. Dose-response experiments performed with (a) steroid hormones, (b) their glucuronides and (c) ouabain-like compounds, emphasize a modulatory effect [activation of the Na,K-ATPase at very low concentrations of ligand, inhibition at higher levels; apparent Ki: (a) between 1 and 0.5 mM; (b) between 1 and 0.5 microM; and (c) between 10 and 1 nM; maximum enhancement of the enzymatic activity: (a) +20%; (b) +45%; and (c) +100%]. 3. Displacement experiments of [3H]ouabain evidence a high competition of the ligands towards the cardioglycoside. The relative I50s are: (a) between 1 and 0.5 mM; (b) between 10 and 1 microM; and (c) between 10 and 0.01 nM.

Dissociation of digoxin-like immunoreactivity and Na+,K+-ATPase inhibitory activity in rat plasma

We measured endogenous digitalis-like factor (EDF) in rat plasma during acute saline infusion by two different procedures. Na+,K+-ATPase inhibitory activity in the rat plasma significantly increased during saline loading (7.8 +/- 2.2 vs 2.5 +/- 0.9%, with and without acute saline loading, respectively, p less than 0.05). On the other hand, the plasma digoxin-like immunoreactivity significantly decreased during acute saline loading (16.9 +/- 1.6 vs 32.0 +/- 2.8 pg digoxin equivalents/ml, with and without acute saline loading, respectively, p less than 0.01). These results indicate that the major substances detected by digoxin-like immunoreactivity and direct Na+,K+-ATPase inhibitory activity are completely different, at least in rat plasma.

Free cytosolic calcium in renal proximal tubules from the spontaneously hypertensive rat

Free intracellular calcium was measured in renal proximal tubules obtained from spontaneously hypertensive rats (SHR) and from age-matched Wistar-Kyoto rats (WKY) ingesting a normal diet. Experiments were performed on renal proximal tubule suspensions using fura-2 to monitor cytosolic calcium. In 4-week-old rats, when systolic blood pressure was not significantly different between the two groups, renal proximal tubule cytosolic calcium was similar (143 +/- 28 and 144 +/- 15 nM, respectively). By the age of 5 weeks, cytosolic calcium increased significantly in both SHR and WKY (214 +/- 24 and 262 +/- 34 nM, respectively, p less than 0.05). Calcium, however, was not significantly different between the two groups, even though at this age blood pressure was higher in SHR than in WKY. As compared with values in 4-week-old rats, cytosolic calcium was also found increased in tubules from both SHR and WKY aged 10 to 12 weeks (261 +/- 42 and 279 +/- 30 nM, respectively) and 20 to 24 weeks (263 +/- 42 and 308 +/- 28 nM, respectively). However, no significant differences in cytosolic calcium were found between SHR and WKY even though at these ages systolic blood pressure increased markedly in the SHR. Moreover, regression analysis failed to reveal a correlation between cytosolic calcium and blood pressure when data from either group of rats of all ages studied were pooled. Exposure to ouabain (10(-3) M) to inhibit Na+,K+-adenosine triphosphatase and increase intracellular sodium had no significant effect on cytosolic calcium in tubules from either SHR or WKY (260 +/- 69 and 250 +/- 45 nM, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Ouabain-resistant, amiloride-sensitive Na+-K+ pumping activity and morphological changes are inducible

The functional expression of a ouabain-resistance gene has been studied in a transfected cell line, OR-6 cells. These cells possess a ouabain-inhibitable, amiloride-resistant Na+-K+ pump under control conditions. They can be induced by brief culture in the presence of low concentrations of ouabain to express a ouabain-resistant, amiloride-sensitive Na+-K+ pumping activity. They revert to the uninduced phenotype shortly after removal of ouabain from the culture medium. When placed in low-potassium, low-serum, or dibutyryl adenosine 3'-5'-cyclic monophosphate-containing media, these cells produce long cellular extensions. Thus a single inducible gene appears to regulate sensitivity of the Na+-K+ pumping activity to cardiac glycosides and to amiloride, and it may be related to important characteristics of cellular morphology.