Calcium ion as cellular messenger

Mitochondrial Electron Transfer Chain Activation in Atrophic Muscle: Implications for Calcium Signaling and Chondrocyte Apoptosis in Osteoarthritis

Skeletal muscle wasting directly impacts the stability of the knee joint, leading to the development of osteoarthritis (OA). However, the underlying mechanism of the interaction between skeletal muscle and cartilage remains unclear. Therefore, the cross-talk between skeletal muscle and cartilage was investigated in rat models of muscle atrophy and the combination of OA and muscle atrophy through gait analysis, grip strength testing, micro-CT, and histological staining. The underlying mechanism was identified through metabolomics, RNA-sequencing, and verification experiments. It is first confirmed that skeletal muscle wasting induces reduction of joint function and the acceleration of cartilage injury. Furthermore, OA chondrocytes exhibited worsened injury when co-cultured with atrophied muscle. Mechanistically, metabolomics revealed the differential metabolites in muscle mainly enriched mitochondrial electron transport chain signaling pathway, which is the primary source of reactive oxygen species (ROS). RNA-sequencing of cartilage combined with verification experiments further indicated that the calcium signaling pathway in injured cartilage was activated, leading to the increase in chondrocyte apoptosis and inflammation, which attributed to the elevated levels of ROS in muscle atrophy, which stimulates synovium to further produce ROS and then release it into knee joint fluid. These observations suggest that elevated ROS levels in atrophied muscle may activate the calcium signaling pathway, leading to the increase of chondrocyte apoptosis, and ultimately exacerbate OA, which have potential to be a novel therapeutic target for OA treatment.

MICU1 is the nexus for CaV3.3 regulation of mitochondrial calcium, redox balance and chondrocyte viability

Voltage-gated calcium channels are emerging regulators of cellular homeostasis, but their molecular interplay with mitochondrial bioenergetics in chondrocytes remains poorly characterized. This study elucidates how the T-type calcium channel CaV3.3 governs mitochondrial calcium-redox coupling through structural interactions with MICU1, the regulatory subunit of the mitochondrial calcium uniporter (MCU) complex. The absence of the CaV3.3 precipitated mitochondrial ultrastructural disorganization characterized, coupled with MICU1 downregulation and consequent loss of MCU gating fidelity. Through integrated transcriptomic-proteomic profiling and live-cell imaging, we demonstrate that CaV3.3 deficiency induces pathological mitochondrial calcium influx, triggering Reactive oxygen species (ROS) overproduction and bioenergetic collapse, these metabolic derangements activated intrinsic apoptosis. Notably, lentiviral overexpression of MICU1 in CaV3.3 knockout cells restored the mitochondrial calcium set point and inhibited ROS burst, while rescued cell proliferation and inhibited apoptosis execution. Our findings establish CaV3.3 as a redox rheostat coordinating MICU1-mediated mitochondrial calcium buffering, with direct implications for cartilage matrix maintenance and osteoarthritis therapy targeting calcium-handling macromolecules.

Cross-Sectional Associations between Clinical Biochemistry and Nutritional Biomarkers and Sarcopenic Indices of Skeletal Muscle in the Baltimore Longitudinal Study of Aging

BACKGROUND

Investigating relationships between nutritional and clinical biochemistry biomarkers and skeletal muscle mass, strength and function (sarcopenic indices) may 1) highlight micronutrients of interest for potential preventive or treatment strategies for sarcopenia, or 2) highlight biomarkers that may be useful for identifying individuals at risk of sarcopenia.

OBJECTIVES

Investigate associations between nutritional biomarkers (vitamin D, vitamin B12, folate, magnesium, potassium, calcium, and iron), clinical biomarkers (hemoglobin, ferritin, albumin, creatinine, and hemoglobin A1c: HbA1c), and sarcopenic indices (appendicular lean mass: ALM); height-adjusted ALM: ALMht; fat-free mass as a percentage of total body weight; extended short physical performance battery score: extSPPB; height-adjusted hand grip strength: HGSht; height-adjusted knee extension concentric strength, and; height-adjusted knee extension isometric strength) in males and females.

METHODS

Using multivariable linear regression analysis, we investigated cross-sectional associations between biomarkers and sarcopenic indices in data collected from 1761 participants (age 22-103 y) from the Baltimore Longitudinal Study of Aging.

RESULTS

Hemoglobin was positively associated with ALM (β = 0.20, P = 0.021), HGSht (β = 0.25, P = 0.001), and extSPPB (β = 0.13, P = 0.024) in males, and with extSPPB in females (β = 0.15, P = 0.019). In males, serum iron was positively associated with ALMht (β = 0.0021, P = 0.038) and extSPPB (β = 0.0043, P = 0.045). In females, ferritin was positively associated with knee-extension strength measurements. Serum creatinine was positively associated with lean mass measures in males and females and with muscle strength and function measures in males with normal renal function (estimated glomerular filtration rate ≥60 mL/min/1.73 m2). In males, high HbA1c was associated with lower ALMht (β = -0.21, P = 0.023), extSPPB (β = -0.40, P = 0.027), and HGSht (β = -0.56, P = 0.031). In males and females, magnesium was positively associated with extSPPB, and potassium was positively associated with measures of knee-extension strength.

CONCLUSIONS

The associations found between measures of iron status and creatinine and sarcopenic indices, in males in particular, indicate potential importance for muscle health. Future longitudinal and intervention studies are warranted to confirm these findings.

Optogenetics and chemogenetics: key tools for modulating neural circuits in rodent models of depression

Optogenetics and chemogenetics are emerging neuromodulation techniques that have attracted significant attention in recent years. These techniques enable the precise control of specific neuronal types and neural circuits, allowing researchers to investigate the cellular mechanisms underlying depression. The advancement in these techniques has significantly contributed to the understanding of the neural circuits involved in depression; when combined with other emerging technologies, they provide novel therapeutic targets and diagnostic tools for the clinical treatment of depression. Additionally, these techniques have provided theoretical support for the development of novel antidepressants. This review primarily focuses on the application of optogenetics and chemogenetics in several brain regions closely associated with depressive-like behaviors in rodent models, such as the ventral tegmental area, nucleus accumbens, prefrontal cortex, hippocampus, dorsal raphe nucleus, and lateral habenula and discusses the potential and challenges of optogenetics and chemogenetics in future research. Furthermore, this review discusses the potential and challenges these techniques pose for future research and describes the current state of research on sonogenetics and odourgenetics developed based on optogenetics and chemogenetics. Specifically, this study aimed to provide reliable insights and directions for future research on the role of optogenetics and chemogenetics in the neural circuits of depressive rodent models.

TROP2 promotes the proliferation of triple-negative breast cancer cells via calcium ion-dependent ER stress signaling pathway

OBJECTIVE

To explore the molecular mechanisms of tumor-associated calcium signal transduction factor 2 (TROP2) affecting the occurrence and development of triple-negative breast cancer (TNBC).

METHODS

The TCGA database, immunohistochemical staining, and qRT-PCR were used to analyze the expression of TROP2 in TNBC tissues and cells. The protein expressions of TROP2 and inositol 1,4,5-trisphosphate receptor (IP3R) after TROP2 knockdown were detected by western blot (WB). Cell proliferation was detected by CCK8 and colony formation assay, Annexin V-APC/PI flow cytometry was used to detect apoptosis, and intracellular calcium ion (Ca2+) was detected by flow cytometry with Fura 2-AM fluorescent probe. Finally, the morphological changes of the endoplasmic reticulum (ER) were observed by transmission electron microscopy, and the expression of ER stress (ERS)-related proteins was detected by WB and immunofluorescence staining.

RESULTS

TROP2 was up-regulated in TNBC tumor tissues and cells. Silencing TROP2 decreased the proliferation rate and clone formation number, and increased the apoptosis rate and the Ca2+ level in TNBC cells. These phenomena were reversed after the addition of 2-APB. In addition, after TROP2 knockdown, the expressions of IP3R and ERS-related proteins were up-regulated, the ER was cystic dilated, and ERS was activated. And the addition of 2-APB significantly inhibited the activation of ERS induced by TROP2 knockdown.

CONCLUSION

TROP2 regulated the proliferation and apoptosis of TNBC cells through a Ca2+-dependent ERS signaling pathway.

Ca2+ Overload Decreased Cellular Viability in Magnetic Hyperthermia without a Macroscopic Temperature Rise

Magnetic hyperthermia is a crucial medical engineering technique for treating diseases, which usually uses alternating magnetic fields (AMF) to interplay with magnetic substances to generate heat. Recently, it has been found that in some cases, there is no detectable temperature increment after applying an AMF, which caused corresponding effects surprisingly. The mechanisms involved in this phenomenon are not yet fully understood. In this study, we aimed to explore the role of Ca2+ overload in the magnetic hyperthermia effect without a perceptible temperature rise. A cellular system expressing the fusion proteins TRPV1 and ferritin was prepared. The application of an AMF (518 kHz, 16 kA/m) could induce the fusion protein to release a large amount of iron ions, which then participates in the production of massive reactive oxygen radicals (ROS). Both ROS and its induced lipid oxidation enticed the opening of ion channels, causing intracellular Ca2+ overload, which further led to decreased cellular viability. Taken together, Ca2+ overload triggered by elevated ROS and the induced oxidation of lipids contributes to the magnetic hyperthermia effect without a perceptible temperature rise. These findings would be beneficial for expanding the application of temperature-free magnetic hyperthermia, such as in cellular and neural regulation, design of new cancer treatment methods.

A Silicon-Based Field-Effect Biosensor for Drug-Induced Cardiac Extracellular Calcium Ion Change Detection

Calcium ions participate in the regulation of almost all biological functions of the body, especially in cardiac excitation-contraction coupling, acting as vital signaling through ion channels. Various cardiovascular drugs exert their effects via affecting the ion channels on the cell membrane. The current strategies for calcium ion monitoring are mainly based on fluorescent probes, which are commonly used for intracellular calcium ion detection (calcium imaging) and cannot achieve long-term monitoring. In this work, an all-solid-state silicone-rubber ion-sensitive membrane was fabricated on light-addressable potentiometric sensors to establish a program-controlled field-effect-based ion-sensitive light-addressable potentiometric sensor (LAPS) platform for extracellular calcium ion detection. L-type calcium channels blocker verapamil and calcium channel agonist BayK8644 were chosen to explore the effect of ion channel drugs on extracellular calcium ion concentration in HL-1 cell lines. Simultaneously, microelectrode array (MEA) chips were employed to probe the HL-1 extracellular field potential (EFP) signals. The Ca2+ concentration and EFP parameters were studied to comprehensively evaluate the efficacy of cardiovascular drugs. This platform provides more dimensional information on cardiovascular drug efficacy that can be utilized for accurate drug screening.

Transcription factors SltA and CrzA reversely regulate calcium homeostasis under calcium-limited conditions

IMPORTANCE

Calcium ions are ubiquitous intracellular signaling molecules for many signaling pathways regulating the fungal response to stress and antifungal drugs. The concentration of intracellular calcium is tightly regulated in its storage, release, and distribution. CrzA is the best-studied transcription factor that regulates this process under sufficient calcium or other external signals. However, CrzA was excluded from nuclei and then lost transcriptional activation under calcium-limited conditions. The regulators in the Ca2+ signaling pathway under calcium-limited conditions remain unclear. Here, we identified SltA as a key regulator in the Ca2+ signaling pathway under calcium-limited conditions, and the underlying mechanisms were further explored in Aspergillus fumigatus. These findings reveal a transcriptional control pathway that precisely regulates calcium homeostasis under calcium-limited conditions.

Essential Minerals and Metabolic Adaptation of Immune Cells

Modern lifestyles deviated considerably from the ancestral routines towards major shifts in diets and increased sedentarism. The trace elements status of the human body is no longer adequately supported by micronutrient-inferior farmed meats and crop commodities produced by the existing agricultural food systems. This is particular evident in the increased obesogenic adipogenesis and low-grade inflammation that fails to resolve with time. The metabolically restrictive environment of the inflamed tissues drives activation and proliferation of transient and resident populations of immune cells in favor of pro-inflammatory phenotypes, as well as a part of the enhanced autoimmune response. As different stages of the immune activation and resolution depend on the availability of specific minerals to maintain the structural integrity of skin and mucus membranes, activation and migration of immune cells, activation of the complement system, and the release of pro-inflammatory cytokines and chemokines, this review discusses recent advances in our understanding of the contribution of select minerals in optimizing the responses of innate and adaptive immune outcomes. An abbreviated view on the absorption, transport, and delivery of minerals to the body tissues as related to metabolic adaptation is considered.

Influence of Calcium Resonance-Tuned Low-Frequency Magnetic Fields on Daphnia magna

A biophysical model for calculating the effective parameters of low-frequency magnetic fields was developed by Lednev based on summarized empirical data. According to this model, calcium ions as enzyme cofactors can be the primary target of low-frequency magnetic fields with different parameters tuned to calcium resonance. However, the effects of calcium-resonant combinations of static and alternating magnetic fields that correspond to Lednev's model and differ by order in frequency and intensity were not studied. It does not allow for confidently discussing the primary targets of low-frequency magnetic fields in terms of the magnetic influence on ions-enzyme cofactors. To clarify this issue, we examined the response of freshwater crustaceans Daphnia magna to the impact of combinations of magnetic fields targeted to calcium ions in enzymes according to Lednev's model that differ in order of magnitude. Life-history traits and biochemical parameters were evaluated. Exposure of daphnids to both combinations of magnetic fields led to a long-term delay of the first brood release, an increase in the brood size, a decrease in the number of broods, and the period between broods. The amylolytic activity, proteolytic activity, and sucrase activity significantly decreased in whole-body homogenates of crustaceans in response to both combinations of magnetic fields. The similarity in the sets of revealed effects assumes that different magnetic fields tuned to calcium ions in biomolecules can affect the same primary molecular target. The results suggest that the low-frequency magnetic fields with parameters corresponding to Lednev's model of interaction between biological molecules and ions can remain effective with a significant decrease in the static magnetic background.

Piezo1-Mediated Mechanotransduction Promotes Cardiac Hypertrophy by Impairing Calcium Homeostasis to Activate Calpain/Calcineurin Signaling

[Figure: see text].

Gender Differences in Hemocyte Immune Parameters of Hong Kong Oyster Crassostrea hongkongensis During Immune Stress

Gender differences in individual immune responses to external stimuli have been elucidated in many invertebrates. However, it is unclear if gender differences do exist in the Hong Kong oyster Crassostrea hongkongensis, one of the most valuable marine species cultivated along the coast of South China. To clarify this, we stimulated post-spawning adult C. hongkongensis with Vibrio harveyi and lipopolysaccharide (LPS). Gender-based differences in some essential functional parameters of hemocytes were studied via flow cytometry. Obvious gender-, subpopulation-, and immune-specific alterations were found in the hemocyte immune parameters of C. hongkongensis. Three hemocyte subpopulations were identified: granulocytes, semi-granulocytes, and agranulocytes. Granulocytes, the chief phagocytes and major producers of esterase, reactive oxygen species, and nitric oxide, were the main immunocompetent hemocytes. Immune parameter alterations were notable in the accumulation of granulocyte esterase activities, lysosomal masses, nitric oxide levels, and granulocyte numbers in male oysters. These results suggest that post-spawning-phase male oysters possess a more powerful immune response than females. Gender and subpopulation differences in bivalve immune parameters should be considered in the future analysis of immune parameters when studying the impact of pathogenic or environmental factors.

Transcriptional changes of Pacific oyster Crassostrea gigas reveal essential role of calcium signal pathway in response to CO2-driven acidification

There is increasing evidence that ocean acidification (OA) has a significant impact on marine organisms. However, the ability of most marine organisms to acclimate to OA and the underlying mechanisms are still not well understood. In the present study, whole transcriptome analysis was performed to compare the impacts of short- (7 days, named as short group) and long- (60 days, named as long group) term CO₂ exposure (pH 7.50) on Pacific oyster Crassostrea gigas. The responses of C. gigas to short- and long-term CO₂ exposure shared common mechanisms in metabolism, membrane-associated transportation and binding processes. Long-term CO₂ exposure induced significant expression of genes involved in DNA or RNA binding, indicating the activated transcription after long-term CO₂ exposure. Oysters in the short-term group underwent significant intracellular calcium variation and oxidative stress. In contrast, the intracellular calcium, ROS level in hemocytes and H₂O₂ in serum recovered to normal levels after long-term CO₂ exposure, suggesting the compensation of physiological status and mutual interplay between calcium and oxidative level. The compensation was supported by the up-regulation of a series of calcium binding proteins (CBPs) and calmodulins (CaMs) related signal pathway. The results provided valuable information to understand the molecular mechanism underlying the responses of Pacific oyster to the acidified ocean and might have implications for predicting the possible effects of global climate changes on oyster aquaculture.

MGP Promotes Colon Cancer Proliferation by Activating the NF-κB Pathway through Upregulation of the Calcium Signaling Pathway

Matrix Gla protein (MGP), an extracellular matrix protein, is mainly associated with the inhibition of calcification in skeleton, coronary artery, and kidney, and more recently it has also been implicated in cancer. However, the biological function of MGP inside cancer cells and its role in colon cancer (CC) remain largely unknown. MGP expression and its association with clinicopathologic characteristics in CC were analyzed by immunohistochemistry and verified by Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets. The effects of MGP on CC cell proliferation were evaluated via knockdown and overexpression experiments in vitro. Mechanisms of MGP in CC were explored by western blots, quantitative real-time PCR, Fluo-3 AM staining, Rhod-2 AM staining, immunofluorescence, and other techniques. Our study confirmed that MGP was upregulated in different stages of CC and associated with a worse prognosis. MGP could enrich intracellular free Ca2+ concentration and promote nuclear factor κB (NF-κB)/p65 phosphorylation, activating the expression of c-MYC, ICAM-1, and VEGFA. Furthermore, the reduction of intracellular free Ca2+ concentration and the subsequent growth inhibition effect on CC cells induced by small interfering RNA targeting MGP (siMGP) could be rescued by a higher calcium concentration environment. Therefore, MGP promotes the growth and proliferation of CC cells by enriching intracellular calcium concentration and activating the NF-κB pathway, and it could serve as a potential prognostic biomarker in CC patients.

The Role of Circular RNAs in Cerebral Ischemic Diseases: Ischemic Stroke and Cerebral Ischemia/Reperfusion Injury

Cerebral ischemic diseases including ischemic stroke and cerebral ischemia reperfusion injury can result in serious dysfunction of the brain, which leads to extremely high mortality and disability. There are no effective therapeutics for cerebral ischemic diseases to date. Circular RNAs are a kind of newly investigated noncoding RNAs. It is reported that circular RNAs are enriched in multiple organs, especially abundant in the brain, which indicates that circular RNAs may be involved in cerebral physiological and pathological processes. In this chapter, we will firstly review the pathophysiology, underlying mechanisms, and current treatments of cerebral ischemic diseases including ischemic stroke and cerebral ischemia/reperfusion injury. Secondly, the characteristics and function of circular RNAs will be outlined, and then we are going to introduce the roles circular RNAs play in human diseases. Finally, we will summarize the function of circular RNAs in cerebral ischemic diseases.

Role of FK506-binding protein in Ca2+ spark regulation

The elementary Ca²⁺ release events, Ca²⁺ sparks, has been found for a quarter of century. However, the molecular regulation of the spark generator, the ryanodine receptor (RyR) on the sarcoplasmic reticulum, remains obscure. Although each subunit of the RyR homotetramer has a site for FK506-binding protein (FKBP), the role of FKBPs in modifying RyR Ca²⁺ sparks has been debated for long. One of the reasons behind the controversy is that most previous studies detect spontaneous sparks, where the mixture with out-of-focus events and local wavelets prevents an accurate characterization of Ca²⁺ sparks. In the present study, we detected Ca²⁺ sparks triggered by single L-type Ca²⁺ channels (LCCs) under loose-seal patch clamp conditions in FK506-treated or FKBP12.6 knockout cardiomyocytes. We found that FKBP dissociation both by FK506 and by rapamycin decreased the Ca²⁺ spark amplitude in ventricular cardiomyocytes. This change was neither due to decreased releasable Ca²⁺ in the sarcoplasmic reticulum, nor explained by changed RyR sensitivity. Actually FK506 increased the LCC-RyR coupling probability and curtailed the latency for an LCC to trigger a RyR Ca²⁺ spark. FKBP12.6 knockout had similar effects as FK506/rapamycin treatment, indicating that the decreased spark amplitude was attributable to the dissociation of FKBP12.6 rather than FKBP12. We also explained how decreased amplitude of spontaneous sparks after FKBP dissociation sometimes appears to be increased or unchanged due to inappropriate data processing. Our results provided firm evidence that without the inter-RyR coordination by functional FKBP12.6, the RyR recruitment during a Ca²⁺ spark would be compromised despite the sensitization of individual RyRs.

Affinity-based fluorescence polarization assay for screening molecules acting on insect ryanodine receptors

A fluorescence polarization assay was developed for studying affinity binding of active molecules to specific binding site on insect ryanodine receptor.

Artemisinin mimics calorie restriction to trigger mitochondrial biogenesis and compromise telomere shortening in mice

Calorie restriction is known to extend lifespan among organisms by a debating mechanism underlying nitric oxide-driven mitochondrial biogenesis. We report here that nitric oxide generators including artemisinin, sodium nitroprusside, and L-arginine mimics calorie restriction and resembles hydrogen peroxide to initiate the nitric oxide signaling cascades and elicit the global antioxidative responses in mice. The large quantities of antioxidant enzymes are correlated with the low levels of reactive oxygen species, which allow the down-regulation of tumor suppressors and accessory DNA repair partners, eventually leading to the compromise of telomere shortening. Accompanying with the up-regulation of signal transducers and respiratory chain signatures, mitochondrial biogenesis occurs with the elevation of adenosine triphosphate levels upon exposure of mouse skeletal muscles to the mimetics of calorie restriction. In conclusion, calorie restriction-triggered nitric oxide provides antioxidative protection and alleviates telomere attrition via mitochondrial biogenesis, thereby maintaining chromosomal stability and integrity, which are the hallmarks of longevity.