Differential expression of calcium transport genes caused by COMT inhibition in the duodenum, kidney and placenta of pregnant mice

Preeclampsia and transport of ions and small molecules: A literature review

Preeclampsia (PE) is a prevalent obstetric complication affecting approximately 3-5% of pregnancies worldwide and is a major cause of maternal and perinatal morbidity and mortality. Preeclampsia is considered a disease of the endothelial system that can progress to eclampsia, characterized by seizures. Early diagnosis and appropriate management are crucial to improving maternal and fetal outcomes, as preeclampsia can lead to severe complications such as placental abruption, fetal growth restriction, and stroke. The pathophysiology of PE is complex, involving a combination of genetic, acquired, and immunological factors. A central feature of the condition is inadequate placentation and impaired uteroplacental perfusion, leading to local hypoxia, endothelial dysfunction, vasoconstriction, and immunological dysregulation. Recent evidence suggests that dysregulation of ion transporters may play a significant role in the adaptation of uterine circulation during placentation. These transporters are essential for maintaining maternal-fetal homeostasis, influencing processes such as nutrient exchange, hormone synthesis, trophoblast cell migration, and the function of smooth muscle cells in blood vessels. In preeclampsia, adverse conditions like hypoxia and oxidative stress result in the downregulation of ion, solute, and water transporters, impairing their function. This review focuses on membrane transporters involved in PE, discussing functional alterations and their physiological implications. The goal of this investigation is to enhance understanding of how dysregulation of ion and small molecule transporters contributes to the development and progression of preeclampsia, underscoring the importance of exploring these signaling pathways for potential therapeutic interventions.

Calcium selective channel TRPV6: Structure, function, and implications in health and disease

Calcium-selective channel TRPV6 (Transient Receptor Potential channel family, Vanilloid subfamily member 6) belongs to the TRP family of cation channels and plays critical roles in transcellular calcium (Ca2+) transport, reuptake of Ca2+ into cells, and maintaining a local low Ca2+ environment for certain biological processes. Recent crystal and cryo-electron microscopy-based structures of TRPV6 have revealed mechanistic insights on how the protein achieves Ca2+ selectivity, permeation, and inactivation by calmodulin. The TRPV6 protein is expressed in a range of epithelial tissues such as the intestine, kidney, placenta, epididymis, and exocrine glands such as the pancreas, prostate and salivary, sweat, and mammary glands. The TRPV6 gene is a direct transcriptional target of the active form of vitamin D and is efficiently regulated to meet the body's need for Ca2+ demand. In addition, TRPV6 is also regulated by the level of dietary Ca2+ and under physiological conditions such as pregnancy and lactation. Genetic models of loss of function in TRPV6 display hypercalciuria, decreased bone marrow density, deficient weight gain, reduced fertility, and in some cases alopecia. The models also reveal that the channel plays an indispensable role in maintaining maternal-fetal Ca2+ transport and low Ca2+ environment in the epididymal lumen that is critical for male fertility. Most recently, loss of function mutations in TRPV6 gene is linked to transient neonatal hyperparathyroidism and early onset chronic pancreatitis. TRPV6 is overexpressed in a wide range of human malignancies and its upregulation is strongly correlated to tumor aggressiveness, metastasis, and poor survival in selected cancers. This review summarizes the current state of knowledge on the expression, structure, biophysical properties, function, polymorphisms, and regulation of TRPV6. The aberrant expression, polymorphisms, and dysfunction of this protein linked to human diseases are also discussed.

Comparison of steroid hormones in three different preeclamptic models

Preeclampsia (PE) is a complication of pregnancy and is characterized by hypertension and proteinuria, threatening both the mother and the fetus. However, the etiology of PE has not yet been fully understood. Since the imbalance of steroid hormones is associated with the pathogenesis of PE, investigating steroidogenic mechanisms under various PE conditions is essential to understand the entire spectrum of pregnancy disorders. Therefore, the current study established three PE in vitro and in vivo models, and compared the levels of steroid hormones and steroidogenic enzymes within them. In cellular PE models induced by hypoxia, N‑nitro‑L‑arginine methyl ester hydrocholride (L‑NAME) and catechol‑o‑methyltransferase inhibitor, the levels of steroid hormones, including pregnenolone (P5), progesterone (P4), dehydroepiandrosterone (DHEA) and testosterone tended to decrease during steroidogenesis. Injection of L‑NAME in pregnant rats led to a reduction in the levels of estradiol and P4 through regulation of cholesterol side‑chain cleavage enzyme (CYP11A1) and 3β‑hydroxysteroid dehydrogenase/δ5 4‑isomerase type 1 (HSD3B1), whereas rats treated with COMT‑I exhibited elevated levels of P5 and DHEA by regulation of the CYP11A1 and aromatase cytochrome P450 (CYP19A1) in the placenta and plasma. The reduced uterine perfusion pressure operation decreased CYP11A1 and increased CYP19A1 expression in placental tissues, whereas steroid hormone levels were not altered. In conclusion, the results of the present study suggest that the induction of PE conditions dysregulates the steroid hormones via regulation of steroidogenic enzymes, depending on specific PE symptoms. These findings can contribute to the development of novel diagnostic and therapeutic modalities for PE, by monitoring and supplying appropriate levels of steroid hormones.

Live-Cell Cardiac-Specific High-Throughput Screening Platform for Drug-Like Molecules that Enhance Ca2+ Transport

We engineered a concatenated fluorescent biosensor and dual-wavelength fluorescence lifetime (FLT) detection, to perform high-throughput screening (HTS) in living cells for discovery of potential heart-failure drugs. Heart failure is correlated with insufficient activity of the sarcoplasmic reticulum Ca-pump (SERCA2a), often due to excessive inhibition by phospholamban (PLB), a small transmembrane protein. We sought to discover small molecules that restore SERCA2a activity by disrupting this inhibitory interaction between PLB and SERCA2a. Our approach was to fluorescently tag the two proteins and measure fluorescence resonance energy transfer (FRET) to detect changes in binding or structure of the complex. To optimize sensitivity to these changes, we engineered a biosensor that concatenates the two fluorescently labeled proteins on a single polypeptide chain. This SERCA2a-PLB FRET biosensor construct is functionally active and effective for HTS. By implementing 2-wavelength FLT detection at extremely high speed during primary HTS, we culled fluorescent compounds as false-positive Hits. In pilot screens, we identified Hits that alter the SERCA2a-PLB interaction, and a newly developed secondary calcium uptake assay revealed both activators and inhibitors of Ca-transport. We are implementing this approach for large-scale screens to discover new drug-like modulators of SERCA2a-PLB interactions for heart failure therapeutic development.

Network Systems Pharmacology-Based Mechanism Study on the Beneficial Effects of Vitamin D against Psychosis in Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease with significant financial costs and negative impacts on quality of life. Psychotic symptoms, i.e., the presence of delusions and/or hallucinations, is a frequent complication of AD. About 50% of AD patients will develop psychotic symptoms (AD with Psychosis, or AD + P) and these patients will experience an even more rapid cognitive decline than AD patients without psychosis (AD-P). In a previous analysis on medication records of 776 AD patients, we had shown that use of Vitamin D was associated with delayed time to psychosis in AD patients and Vitamin D was used more by AD-P than AD + P patients. To explore the potential molecular mechanism behind our findings, we applied systems pharmacology approaches to investigate the crosstalk between AD and psychosis. Specifically, we built protein-protein interaction (PPI) networks with proteins encoded by AD- and psychosis-related genes and Vitamin D-perturbed genes. Using network analysis we identified several high-impact genes, including NOTCH4, COMT, CACNA1C and DRD3 which are related to calcium homeostasis. The new findings highlight the key role of calcium-related signaling pathways in AD + P development and may provide a new direction and facilitate hypothesis generation for future drug development.

Effect of Chlorella Pyrenoidosa Protein Hydrolysate-Calcium Chelate on Calcium Absorption Metabolism and Gut Microbiota Composition in Low-Calcium Diet-Fed Rats

In our current investigation, we evaluated the effect of Chlorella pyrenoidosa protein hydrolysate (CPPH) and Chlorella pyrenoidosa protein hydrolysate-calcium chelate (CPPH-Ca) on calcium absorption and gut microbiota composition, as well as their in vivo regulatory mechanism in SD rats fed low-calcium diets. Potent major compounds in CPPH were characterized by HPLC-MS/MS, and the calcium-binding mechanism was investigated through ultraviolet and infrared spectroscopy. Using high-throughput next-generation 16S rRNA gene sequencing, we analyzed the composition of gut microbiota in rats. Our study showed that HCPPH-Ca increased the levels of body weight gain, serum Ca, bone activity, bone mineral density (BMD) and bone mineral content (BMC), while decreased serum alkaline phosphatase (ALP) and inhibited the morphological changes of bone. HCPPH-Ca up-regulated the gene expressions of transient receptor potential cation V5 (TRPV5), TRPV6, calcium-binding protein-D9k (CaBP-D9k) and a calcium pump (plasma membrane Ca-ATPase, PMCA1b). It also improved the abundances of Firmicutes and Lactobacillus. Bifidobacterium and Sutterella were both positively correlated with calcium absorption. Collectively, these findings illustrate the potential of HCPPH-Ca as an effective calcium supplement.

Establishing life is a calcium-dependent TRiP: Transient receptor potential channels in reproduction

Calcium plays a key role in many different steps of the reproduction process, from germ cell maturation to placental development. However, the exact function and regulation of calcium throughout subsequent reproductive events remains rather enigmatic. Successful pregnancy requires the establishment of a complex dialogue between the implanting embryo and the endometrium. On the one hand, endometrial cell will undergo massive changes to support an implanting embryo, including stromal cell decidualization. On the other hand, trophoblast cells from the trophectoderm surrounding the inner cell mass will differentiate and acquire new functions such as hormone secretion, invasion and migration. The need for calcium in the different gestational processes implicates the presence of specialized ion channels to regulate calcium homeostasis. The superfamily of transient receptor potential (TRP) channels is a class of calcium permeable ion channels that is involved in the transformation of extracellular stimuli into the influx of calcium, inducing and coordinating underlying signaling pathways. Although the necessity of calcium throughout reproduction cannot be negated, the expression and functionality of TRP channels throughout gestation remains elusive. This review provides an overview of the current evidence regarding the expression and function of TRP channels in reproduction.

NCKX3 was compensated by calcium transporting genes and bone resorption in a NCKX3 KO mouse model

Gene knockout is the most powerful tool for determination of gene function or permanent modification of the phenotypic characteristics of an animal. Existing methods for gene disruption are limited by their efficiency, time required for completion and potential for confounding off-target effects. In this study, a rapid single-step approach to knockout of a targeted gene in mice using zinc-finger nucleases (ZFNs) was demonstrated for generation of mutant (knockout; KO) alleles. Specifically, ZFNs to target the sodium/calcium/potassium exchanger3 (NCKX3) gene in C57bl/6j were designed using the concept of this approach. NCKX3 KO mice were generated and the phenotypic characterization and molecular regulation of active calcium transporting genes was assessed when mice were fed different calcium diets during growth. General phenotypes such as body weight and plasma ion level showed no distinct abnormalities. Thus, the potassium/sodium/calcium exchanger of NCKX3 KO mice proceeded normally in this study. As a result, the compensatory molecular regulation of this mechanism was elucidated. Renal TRPV5 mRNA of NCKX3 KO mice increased in both male and female mice. Expression of TRPV6 mRNA was only down-regulated in the duodenum of male KO mice. Renal- and duodenal expression of PTHR and VDR were not changed; however, GR mRNA expression was increased in the kidney of NCKX3 KO mice. Depletion of the NCKX3 gene in a KO mouse model showed loss of bone mineral contents and increased plasma parathyroid hormone, suggesting that NCKX3 may play a role in regulating calcium homeostasis.

Effects of estrogen on esophageal function through regulation of Ca2+-related proteins

BACKGROUND

The calcium ion is important for physiological functions in all tissues and organs and essential to many vital functions, including hormone secretion and muscle contraction. The intracellular concentration of calcium is regulated by calcium related proteins such as CaBP-9k, PMCA1, and NCX1. In this study, we investigated the relationship between calcium regulation and esophageal functions such as mucin secretion and smooth muscle contraction.

METHODS

To evaluate the influence of sex steroid hormones, immature rats were treated for 3 days with estradiol (E2), progesterone (P4), and their antagonists (ICI 182,780, and RU486). Esophageal function, transcription level, and localization of CaBP-9k, PMCA1, NCX1, ERα, and MUC2 were examined in the esophagus.

RESULTS

Transcriptional level of Cabp-9k and Muc2 was increased by E2, but not by P4. CaBP-9k, PMCA1, and MUC2 were mainly localized in the mucosal layer. Acidic mucosubstances in the esophagus were increased by E2 and recovered by ICI treatment. Unlike the expression of Cabp-9k, mRNA levels of Pmca1, Ncx1, and Erα were only decreased in response to E2, and recovered by ICI co-treatment group. The contraction of the esophagus and mRNA level of Mylk were reduced by E2. Overall, E2 upregulated mucus secretion, but downregulated muscle contraction in the esophagus through regulation of the expression of calcium related genes and the resultant intracellular calcium level.

CONCLUSIONS

The regulation of E2 in the function of esophagus may be applied to treat esophageal diseases such as reflux esophagitis, achalasia, and esophageal cancer.

Effects of Octylphenol and Bisphenol A on the Metal Cation Transporter Channels of Mouse Placentas

Octylphenol (OP) and bisphenol A (BPA) are known as endocrine-disrupting chemicals (EDCs). During pregnancy, the expression of steroid hormone receptors is controlled by maternal and fetal nutrition. To evaluate the impact of EDCs during pregnancy, ethinyl estradiol (EE, 0.2 mg/kg/day), OP (50 mg/kg/day), and BPA (50 mg/kg/day) were administered to pregnant mice. The mRNA levels of TRPV6 (transient receptor potential cation channels in subfamily V, member 6) decreased significantly by EE and OP. The PMCA1 (ATPase, Ca⁺⁺ transporting, plasma membrane 1) mRNA and protein levels decreased significantly by EE, OP, and BPA. CTR1 (solute carrier family 31, member 1) and ATP7A (ATPase, Cu⁺⁺ transporting, alpha polypeptide) expression decreased significantly by EE, OP, and BPA. The mRNA levels of IREG1 (iron-regulated transporter, member 1) decreased significantly by EE. Hephaestin (HEPH) mRNA levels decreased significantly by EE, OP, and BPA, and protein levels decreased significantly by BPA. As a result of immunohistochemistry analysis, all cation transporter proteins were found in labyrinth of placenta. To confirm the cytosolic level of cations, levels of cation level in fetal serum were measured. EE, OP, and BPA significantly reduced serum calcium and copper levels, and iron levels were reduced by BPA. Taken together, some EDCs, such as OP and BPA, could modulate the calcium, copper, and iron ion-transporting channels during pregnancy. The fetus relies on the mother for ionic transportation, and, therefore, pregnant women should avoid exposure to cation-channel-disrupting chemicals.

Molecular aspects of intestinal calcium absorption

Intestinal Ca²⁺ absorption is a crucial physiological process for maintaining bone mineralization and Ca²⁺ homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3 steps: the entrance of Ca²⁺ across the brush border membranes (BBM) of enterocytes through epithelial Ca²⁺ channels TRPV6, TRPV5, and Ca_v1.3; Ca²⁺ movement from the BBM to the basolateral membranes by binding proteins with high Ca²⁺ affinity (such as CB_9k); and Ca²⁺ extrusion into the blood. Plasma membrane Ca²⁺ ATPase (PMCA1b) and sodium calcium exchanger (NCX1) are mainly involved in the exit of Ca²⁺ from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1b, since both molecules co-localize and interact. The paracellular pathway consists of Ca²⁺ transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca²⁺ transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca²⁺ absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca²⁺ transport to control values. Calcitriol [1,25(OH)₂D₃] is the major controlling hormone of intestinal Ca²⁺ transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, prolactin, growth hormone, and glucocorticoids apparently also regulate Ca²⁺ transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)₂D₃ production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca²⁺ absorption according to Ca²⁺ demands. Better knowledge of the molecular details of intestinal Ca²⁺ absorption could lead to the development of nutritional and medical strategies for optimizing the efficiency of intestinal Ca²⁺ absorption and preventing osteoporosis and other pathologies related to Ca²⁺ metabolism.