Role of potassium channels in female reproductive system

Genomic and non-genomic action of vitamin D on ion channels - Targeting mitochondria

Recent studies revealed that mitochondria are not only a place of vitamin D3 metabolism but also direct or indirect targets of its activities. This review summarizes current knowledge on the regulation of ion channels from plasma and mitochondrial membranes by the active form of vitamin D3 (1,25(OH)2D3). 1,25(OH)2D3, is a naturally occurring hormone with pleiotropic activities; implicated in the modulation of cell differentiation, and proliferation and in the prevention of various diseases, including cancer. Many experimental data indicate that 1,25(OH)2D3 deficiency induces ionic remodeling and 1,25(OH)2D3 regulates the activity of multiple ion channels. There are two main theories on how 1,25(OH)2D3 can modify the function of ion channels. First, describes the involvement of genomic pathways of response to 1,25(OH)2D3 in the regulation of the expression of the genes encoding channels, their auxiliary subunits, or additional regulators. Interestingly, intracellular ion channels, like mitochondrial, are encoded by the same genes as plasma membrane channels. Therefore, the comprehensive genomic regulation of the channels from these two different cellular compartments we analyzed using a bioinformatic approach. The second theory explores non-genomic pathways of vitamin D3 activities. It was shown, that 1,25(OH)2D3 indirectly regulates enzymes that impact ion channels, change membrane physical properties, or directly bind to channel proteins. In this article, the involvement of genomic and non-genomic pathways regulated by 1,25(OH)2D3 in the modulation of the levels and activity of plasma membrane and mitochondrial ion channels was investigated by an extensive review of the literature and analysis of the transcriptomic data using bioinformatics.

Exploring the therapeutic potential of pomegranate juice for uterine relaxation

BACKGROUND

The effects of pomegranate juice (PJ) and its components on uterine smooth muscle are unknown. Hence, this study unequivocally demonstrates that pomegranate juice (PJ) significantly impacts myometrial function, providing crucial insights into its relaxant properties and their potential therapeutic applications for uterine-related disorders.

RESEARCH DESIGN AND METHODS

Rat uterine smooth muscle horn strips were suspended in Krebs solution organ baths. Contractions were measured isometrically using a transducer (AD instrument Australia). The effects of PJ were evaluated on contractile activity elicited by potassium chloride (KCl 60 Mm) depolarization. Inhibitors of nitric oxide (L-NAME 3 X 10-4), guanylate cyclase (methylene blue 1 X 10-5), and Prostaglandin I2 (indomethacin 3 X 10-5), as well as Potassium Channels blockers, were determined.

RESULTS

The juice at concentrations from 1.5-5 mg/ml significantly decreased the rat uterine horn contraction induced by KCl. The NO, cGMP, and PGI2 inhibitors did not block the relaxation response. Furthermore, the PGI2 inhibitor significantly enhanced the relaxation effects; K+ channel blockers had no inhibitory effects on the relaxation responses. Contrarily, GLIB improved considerably relaxation.

CONCLUSION

Research suggests pomegranate juice's active ingredient may reduce uterine contractions and treat uterotonic disorders, potentially preventing preterm birth and dysmenorrhea. Further research is needed to determine its mechanism of action.

TRIAL REGISTRATION

Code: AEC-013.

Electro-Metabolic Coupling of Cumulus-Oocyte Complex

Oocyte-cumulus cell interaction is essential for oocyte maturation and competence. The bidirectional crosstalk network mediated by gap junctions is fundamental for the metabolic cooperation between these cells. As cumulus cells exhibit a more glycolytic phenotype, they can provide metabolic substrates that the oocyte can use to produce ATP via oxidative phosphorylation. The impairment of mitochondrial activity plays a crucial role in ovarian aging and, thus, in fertility, determining the success or failure of assisted reproductive techniques. This review aims to deepen the knowledge about the electro-metabolic coupling of the cumulus-oocyte complex and to hypothesize a putative role of potassium channel modulators in order to improve fertility, promote intracellular Ca2+ influx, and increase the mitochondrial biogenesis and resulting ATP levels in cumulus cells.

Large conductance voltage-and calcium-activated K+ (BK) channel in health and disease

Large Conductance Voltage- and Calcium-activated K+ (BK) channels are transmembrane pore-forming proteins that regulate cell excitability and are also expressed in non-excitable cells. They play a role in regulating vascular tone, neuronal excitability, neurotransmitter release, and muscle contraction. Dysfunction of the BK channel can lead to arterial hypertension, hearing disorders, epilepsy, and ataxia. Here, we provide an overview of BK channel functioning and the implications of its abnormal functioning in various diseases. Understanding the function of BK channels is crucial for comprehending the mechanisms involved in regulating vital physiological processes, both in normal and pathological conditions, controlled by BK. This understanding may lead to the development of therapeutic interventions to address BK channelopathies.

Assessment of Severity of Long QT Syndrome Phenotype and Risk of Fetal Death

BACKGROUND

It has been postulated that long QT syndrome (LQTS) can cause fetal loss through putative adverse effects of the channelopathy on placenta and myometrial function. The authors aimed to describe the fetal death rate in a population of pregnant women with long QT syndrome and investigate whether women with more severe phenotype had worse fetal outcomes.

METHODS AND RESULTS

The authors retrospectively evaluated fetal outcomes of 64 pregnancies from 23 women with long QT syndrome followed during pregnancy in a tertiary pregnancy and heart disease program. Thirteen of 64 pregnancies (20%) resulted in a fetal loss, 12 miscarriages (19%), and 1 stillbirth (1.6%). Baseline maternal characteristics, including age and use of β-blockers, did not differ between women who experienced a fetal death or not. Maternal corrected QT interval (QTc) was significantly longer in pregnancies that resulted in fetal death compared with live births (median, 518 ms [interquartile range (IQR), 482-519 ms] versus 479 ms [IQR, 454-496 ms], P<0.001). Mothers treated with β-blockers had babies born at term with lower birth weight compared with untreated women (2973±298 g versus 3470±338 g, P=0.002). In addition, the birth weight of babies born at term to treated women with QTc >500 ms was significantly lower compared with women with QTc <500 ms (2783±283 g versus 3084±256 g, P=0.029).

CONCLUSIONS

Women with long QT syndrome with more severe phenotypes have a higher incidence of fetal death. Maternal QTc is longer in pregnancies that result in fetal loss, and the birth weight of babies born to patients taking β-blockers with a QTc >500 ms is lower, suggesting that patients with more marked phenotype may experience worse fetal outcomes.

Genome wide identification and characterization of fertility associated novel CircRNAs as ceRNA reveal their regulatory roles in sheep fecundity

Reproductive traits play a vital role in determining the production efficiency of sheep. Maximizing the production is of paramount importance for breeders worldwide due to the growing population. Circular RNAs (circRNAs) act as miRNA sponges by absorbing miRNA activity through miRNA response elements (MREs) and participate in ceRNA regulatory networks (ceRNETs) to regulate mRNA expression. Despite of extensive research on role of circRNAs as miRNA sponges in various species, their specific regulatory roles and mechanism in sheep ovarian tissue are still not well understood. In this study, we performed whole genome sequencing of circRNAs, miRNA and mRNA employing bioinformatic techniques on ovine tissues of two contrasting sheep breeds "Small tail Han (X_LC) and Dolang sheep (D_LC)", which results into identification of 9,878 circRNAs with a total length of 23,522,667 nt and an average length of 2,381.32 nt. Among them, 44 differentially expressed circRNAs (DECs) were identified. Moreover, correlation between miRNA-mRNA and lncRNA-miRNA provided us with to prediction of miRNA binding sites on nine differentially expressed circRNAs and 165 differentially expressed mRNAs using miRanda. miRNA-mRNA and lncRNA-miRNA pairs with negative correlation were selected to determine the ceRNA score along with positively correlated pairs from lncRNA and mRNA network. Integration of ceRNA score and positively correlated pairs exhibit a significant ternary relationship among circRNAs-miRNA-mRNA demonestrated by ceRNA, comprising of 50 regulatory pairs sharring common nodes and predicted potential differentially expressed circRNAs-miRNAs-mRNAs regulatory axis. Based on functional enrichment analysis shortlisted key ceRNA regulatory pairs associated with reproduction including circRNA_3257-novel579_mature-EPHA3, circRNA_8396-novel130_mature-LOC101102473, circRNA_4140- novel34_mature > novel661_mature-KCNK9, and circRNA_8312-novel339_mature-LOC101110545. Furthermore, expression profiling, functional enrichments and qRT-PCR analysis of key target genes infer their implication in reproduction and metabolism. ceRNA target mRNAs evolutionary trajectories, expression profiling, functional enrichments, subcellular localizations following genomic organizations will provide new insights underlying molecular mechanisms of reproduction, and establish a solid foundation for future research. Graphical abstract summarizing the scheme of study.

Acid-Base, Gas, Ions, and Glucose Analysis in Follicular Fluid in Holstein-Friesian Dairy Cows Is Associated with the Follicle Size in Poland

The lack of fertilization and early pregnancy loss is seen in the quality and maturation of the oocytes. The environment of the first divisions and maturation of the oogonia, which is also a reflection of the quality of the oocyte, is the follicular fluid (FF). Thus, the purpose of this study was to investigate the variations in parameters such as pH, pCO₂, pO₂, standard HCO₃^-, actual HCO₃^-, base excess (BE), base excess of extracellular fluid (BE ecf), ctCO₂, ions: Na⁺, K⁺, actual ionized calcium Ca²⁺, adjusted ionized calcium (at pH 7.4) Ca²⁺ (7.4), Cl^-, anion gap (AnGap), and glucose in FF collected from different size follicles in dairy cattle. The most apparent differences were related to pH, K⁺, and Ca²⁺ 7.4 concentration in comparison to changes in follicle size (p < 0.05). Several trends were also evaluated as an increase in follicular size was followed by an increase in pH, BE, and Ca²⁺ 7.4 value and a decrease in the K⁺ concentration (p < 0.05). In conclusion, there are changes in FF formularies associated with the size of follicles. However, more research is necessary to establish the reference value, which then could be one of the factors describing the quality of the follicle and the developmental potential of the associated oocyte.

Transcriptional profiling of the developing rat ovary following intrauterine exposure to the endocrine disruptors diethylstilbestrol and ketoconazole

Exposure to endocrine-disrupting chemicals (EDCs) during development may cause reproductive disorders in women. Although female reproductive endpoints are assessed in rodent toxicity studies, a concern is that typical endpoints are not sensitive enough to detect chemicals of concern to human health. If so, measured endpoints must be improved or new biomarkers of effects included. Herein, we have characterized the dynamic transcriptional landscape of developing rat ovaries exposed to two well-known EDCs, diethylstilbestrol (DES) and ketoconazole (KTZ), by 3' RNA sequencing. Rats were orally exposed from day 7 of gestation until birth, and from postnatal day 1 until days 6, 14 or 22. Three exposure doses for each chemical were used: 3, 6 and 12 µg/kg bw/day of DES; 3, 6, 12 mg/kg bw/day of KTZ. The transcriptome changed dynamically during perinatal development in control ovaries, with 1137 differentially expressed genes (DEGs) partitioned into 3 broad expression patterns. A cross-species deconvolution strategy based on a mouse ovary developmental cell atlas was used to map any changes to ovarian cellularity across the perinatal period to allow for characterization of actual changes to gene transcript levels. A total of 184 DEGs were observed across dose groups and developmental stages in DES-exposed ovaries, and 111 DEGs in KTZ-exposed ovaries across dose groups and developmental stages. Based on our analyses, we have identified new candidate biomarkers for female reproductive toxicity induced by EDC, including Kcne2, Calb2 and Insl3.

Reproductive Consequences of Electrolyte Disturbances in Domestic Animals

Electrolyte balance is essential to maintain homeostasis in the body. The most crucial electrolytes are sodium (Na+), potassium (K+), magnesium (Mg2+), chloride (Cl−), and calcium (Ca2+). These ions maintain the volume of body fluids, and blood pressure, participate in muscle contractions, and nerve conduction, and are important in enzymatic reactions. The balance is mainly ensured by the kidneys, which are an important organ that regulates the volume and composition of urine, together with which excess electrolytes are excreted. They are also important in the reproductive system, where they play a key role. In the male reproductive system, electrolytes are important in acrosomal reaction and sperm motility. Sodium, calcium, magnesium, and chloride are related to sperm capacitation. Moreover, Mg2+, Ca2+, and Na+ play a key role in spermatogenesis and the maintenance of morphologically normal spermatozoa. Infertility problems are becoming more common. It is known that disturbances in the electrolyte balance lead to reproductive dysfunction. In men, there is a decrease in sperm motility, loss of sperm capacitation, and male infertility. In the female reproductive system, sodium is associated with estrogen synthesis. In the contraction and relaxation of the uterus, there is sodium, potassium, and calcium. Calcium is associated with oocyte activation. In turn, in women, changes in the composition of the follicular fluid are observed, leading to a restriction of follicular growth. Imbalance of oocyte electrolytes, resulting in a lack of oocyte activation and, consequently, infertility.

Mitochondrial potassium channels: A novel calcitriol target

BACKGROUND

Calcitriol (an active metabolite of vitamin D) modulates the expression of hundreds of human genes by activation of the vitamin D nuclear receptor (VDR). However, VDR-mediated transcriptional modulation does not fully explain various phenotypic effects of calcitriol. Recently a fast non-genomic response to vitamin D has been described, and it seems that mitochondria are one of the targets of calcitriol. These non-classical calcitriol targets open up a new area of research with potential clinical applications. The goal of our study was to ascertain whether calcitriol can modulate mitochondrial function through regulation of the potassium channels present in the inner mitochondrial membrane.

METHODS

The effects of calcitriol on the potassium ion current were measured using the patch-clamp method modified for the inner mitochondrial membrane. Molecular docking experiments were conducted in the Autodock4 program. Additionally, changes in gene expression were investigated by qPCR, and transcription factor binding sites were analyzed in the CiiiDER program.

RESULTS

For the first time, our results indicate that calcitriol directly affects the activity of the mitochondrial large-conductance Ca²⁺-regulated potassium channel (mitoBK_Ca) from the human astrocytoma (U-87 MG) cell line but not the mitochondrial calcium-independent two-pore domain potassium channel (mitoTASK-3) from human keratinocytes (HaCaT). The open probability of the mitoBK_Ca channel in high calcium conditions decreased after calcitriol treatment and the opposite effect was observed in low calcium conditions. Moreover, using the AutoDock4 program we predicted the binding poses of calcitriol to the calcium-bound BK_Ca channel and identified amino acids interacting with the calcitriol molecule. Additionally, we found that calcitriol influences the expression of genes encoding potassium channels. Such a dual, genomic and non-genomic action explains the pleiotropic activity of calcitriol.

CONCLUSIONS

Calcitriol can regulate the mitochondrial large-conductance calcium-regulated potassium channel. Our data open a new chapter in the study of non-genomic responses to vitamin D with potential implications for mitochondrial bioenergetics and cytoprotective mechanisms.

The short form of the SUR1 and its functional implications in the damaged brain

Sulfonylurea receptor (SUR) belongs to the adenosine 5′-triphosphate (ATP)-binding cassette (ABC) transporter family; however, SUR is associated with ion channels and acts as a regulatory subunit determining the opening or closing of the pore. Abcc8 and Abcc9 genes code for the proteins SUR1 and SUR2, respectively. The SUR1 transcript encodes a protein of 1582 amino acids with a mass around 140–177 kDa expressed in the pancreas, brain, heart, and other tissues. It is well known that SUR1 assembles with Kir6.2 and TRPM4 to establish K_ATP channels and non-selective cation channels, respectively. Abbc8 and 9 are alternatively spliced, and the resulting transcripts encode different isoforms of SUR1 and SUR2, which have been detected by different experimental strategies. Interestingly, the use of binding assays to sulfonylureas and Western blotting has allowed the detection of shorter forms of SUR (~65 kDa). Identity of the SUR1 variants has not been clarified, and some authors have suggested that the shorter forms are unspecific. However, immunoprecipitation assays have shown that SUR2 short forms are part of a functional channel even coexisting with the typical forms of the receptor in the heart. This evidence confirms that the structure of the short forms of the SURs is fully functional and does not lose the ability to interact with the channels. Since structural changes in short forms of SUR modify its affinity to ATP, regulation of its expression might represent an advantage in pathologies where ATP concentrations decrease and a therapeutic target to induce neuroprotection. Remarkably, the expression of SUR1 variants might be induced by conditions associated to the decrease of energetic substrates in the brain (e.g. during stroke and epilepsy). In this review, we want to contribute to the knowledge of SUR1 complexity by analyzing evidence that shows the existence of short SUR1 variants and its possible implications in brain function.