Mechanical compression influences intracellular Ca2+ signaling in chondrocytes seeded in agarose constructs

2001 ◽  
Vol 90 (4) ◽  
pp. 1385-1391 ◽  
Author(s):  
Susan R. Roberts ◽  
Martin M. Knight ◽  
David A. Lee ◽  
Dan L. Bader
Keyword(s):  
Articular Chondrocytes ◽  
Compressive Strain ◽  
Physiological Role ◽  
Model System ◽  
Mechanical Compression ◽  
Time Points ◽  
Percent Increase ◽  
Intracellular Ca ◽  
Bovine Articular Chondrocytes

Ca2+ signaling forms part of a possible mechanotransduction pathway by which chondrocytes may alter their metabolism in response to mechanical loading. In this study, a well-characterized model system utilizing bovine articular chondrocytes embedded in 4% agarose constructs was used to investigate the effect of physiological mechanical compressive strain applied after 1 and 3 days in culture. The intracellular Ca2+ concentration was measured by use of the ratiometric Ca2+ indicator indo 1-AM and confocal microscopy. A positive Ca2+ response was defined as a percent increase in Ca2+ ratio above a preset threshold. A significantly greater percentage of cells exhibited a positive Ca2+ response in strained constructs compared with unstrained controls at both time points. In strained constructs, treatment with either Ga3+ or EGTA significantly reduced the number of positive Ca2+ responders compared with untreated controls. These results represent an important step in understanding the physiological role of intracellular Ca2+in chondrocytes under mechanical compression.

The Role of IL-1 in Meniscal Tissue Breakdown Following Simulated Partial Meniscectomy

2007 ◽  
Author(s):  
B. Zielinska ◽  
T. Gupta ◽  
T. L. Haut Donahue
Keyword(s):  
Nitric Oxide ◽  
Compressive Strain ◽  
Partial Meniscectomy ◽  
Biochemical Response ◽  
No Production ◽  
Mechanical Compression ◽  
Dynamic Mechanical ◽  
Meniscal Tissue

In a healthy meniscus, the compressive strains are approximately 2–10%. [1] When 30% or more of the tissue is removed during partial meniscectomy, strains increase to approximately 18%. [1] We have previously shown that dynamic compressive strains of 20% to meniscal explants results in an increase in proteoglycan (PG) breakdown, nitric oxide (NO) production, metalloproteinases 1, 3, and 13 (MMP-1, MMP-3, and MMP-13) compared to 0, 5, and 10% compressive strain. [2,3,4] The objective of this study was to determine if interruption of the IL-1 pathway would alter this biochemical response to dynamic mechanical compression.

scholarly journals Role of PKC in the Regulation of the Human Kidney Chloride Channel ClC-Ka

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Andrea Gerbino ◽  
Roberta De Zio ◽  
Daniela Russo ◽  
Luigi Milella ◽  
Serena Milano ◽  
...  
Keyword(s):  
Physiological Role ◽  
Renal Medulla ◽  
Human Kidney ◽  
Inhibitory Effect ◽  
Hek293 Cells ◽  
Whole Cell Patch Clamp ◽  
New Information ◽  
Intracellular Ca ◽  
Accessory Subunit

Abstract The physiological role of the renal ClC-Ka/ClC-K1 channels is to confer a high Cl- permeability to the thin Ascending Limb of Henle (tAL), which in turn is essential for establishing the high osmolarity of the renal medulla that drives water reabsorption from collecting ducts. Here, we investigated by whole-cell patch-clamp measurements on HEK293 cells co-expressing ClC-Ka (tagged with GFP) and the accessory subunit barttin (tagged with m-Cherry) the effect of a natural diuretic extract from roots of Dandelion (DRE), and other compounds activating PKC, such as ATP, on ClC-Ka activity and its membrane localization. Treatment with 400 µg/ml DRE significantly inhibited Cl- currents time-dependently within several minutes. Of note, the same effect on Cl- currents was obtained upon treatment with 100 µM ATP. Pretreatment of cells with either the intracellular Ca2+ chelator BAPTA-AM (30 μM) or the PKC inhibitor Calphostin C (100 nM) reduced the inhibitory effect of DRE. Conversely, 1 µM of phorbol meristate acetate (PMA), a specific PKC activator, mimicked the inhibitory effect of DRE on ClC-Ka. Finally, we found that pretreatment with 30 µM Heclin, an E3 ubiquitin ligase inhibitor, did not revert DRE-induced Cl- current inhibition. In agreement with this, live-cell confocal analysis showed that DRE treatment did not induce ClC-Ka internalization. In conclusion, we demonstrate for the first time that the activity of ClC-Ka in renal cells could be significantly inhibited by the activation of PKC elicited by classical maneuvers, such as activation of purinergic receptors, or by exposure to herbal extracts that activates a PKC-dependent pathway. Overall, we provide both new information regarding the regulation of ClC-Ka and a proof-of-concept study for the use of DRE as new diuretic.

Altered β-adrenergic signal transduction in nonfailing hypertrophied myocytes from Dahl salt-sensitive rats

2000 ◽  
Vol 279 (5) ◽  
pp. H2502-H2508 ◽  
Author(s):  
Kohzo Nagata ◽  
Catherine Communal ◽  
Chee C. Lim ◽  
Mohit Jain ◽  
Thomas M. Suter ◽  
...  
Keyword(s):  
Ventricular Hypertrophy ◽  
Physiological Role ◽  
Cellular Level ◽  
Left Ventricular ◽  
Cell Shortening ◽  
Hypertrophied Myocardium ◽  
Intracellular Ca ◽  
Myocyte Contractility ◽  
Dose Dependent

Desensitization of the β-adrenergic receptor (β-AR) response is well documented in hypertrophied hearts. We investigated whether β-AR desensitization is also present at the cellular level in hypertrophied myocardium, as well as the physiological role of inhibitory G (Gi) proteins and the L-type Ca2+channel in mediating β-AR desensitization. Left ventricular (LV) myocytes were isolated from hypertrophied hearts of hypertensive Dahl salt-sensitive (DS) rats and nonhypertrophied hearts of normotensive salt-resistant (DR) rats. Cells were paced at a rate of 300 beats/min at 37°C, and myocyte contractility and intracellular Ca2+concentration ([Ca2+]i) were simultaneously measured. In response to increasing concentrations of isoproterenol, DR myocytes displayed a dose-dependent augmentation of cell shortening and the [Ca2+]i transient amplitude, whereas hypertrophied DS myocytes had a blunted response of both cell shortening and the [Ca2+]i transient amplitude. Interestingly, inhibition of Gi proteins did not restore β-AR desensitization in DS myocytes. The responses to increases in extracellular Ca2+ and an L-type Ca2+ channel agonist were also similar in both DS and DR myocytes. Isoproterenol-stimulated adenylyl cyclase activity, however, was blunted in hypertrophied myocytes. We concluded that compensated ventricular hypertrophy results in a blunted contractile response to β-AR stimulation, which is present at the cellular level and independent of alterations in inhibitory G proteins and the L-type Ca2+ channel.

Resting calcium influx in airway smooth muscle

2005 ◽  
Vol 83 (8-9) ◽  
pp. 717-723 ◽  
Author(s):  
Luis M Montaño ◽  
Blanca Bazán-Perkins
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Calcium Influx ◽  
Physiological Role ◽  
Resting Membrane Potential ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Influx Pathways

Plasma membrane Ca2+ leak remains the most uncertain of the cellular Ca2+ regulation pathways. During passive Ca2+ influx in non-stimulated smooth muscle cells, basal activity of constitutive Ca2+ channels seems to be involved. In vascular smooth muscle, the 3 following Ca2+ entry pathways contribute to this phenomenon: (i) via voltage-dependent Ca2+ channels, (ii) receptor gated Ca2+ channels, and (iii) store operated Ca2+ channels, although, in airway smooth muscle it seems only 2 passive Ca2+ influx pathways are implicated, one sensitive to SKF 96365 (receptor gated Ca2+ channels) and the other to Ni2+ (store operated Ca2+ channels). Resting Ca2+ entry could provide a sufficient amount of Ca2+ and contribute to resting intracellular Ca2+ concentration ([Ca2+]i), maintenance of the resting membrane potential, myogenic tone, and sarcoplasmic reticulum-Ca2+ refilling. However, further research, especially in airway smooth muscle, is required to better explore the physiological role of this passive Ca2+ influx pathway as it could be involved in airway hyperresponsiveness.Key words: basal Ca2+ entry, constitutive Ca2+ channels, airway and vascular smooth muscle, SKF 96365, Ni2+.

Molecular Nature and Physiological Role of the Mitochondrial Calcium Uniporter Channel

2020 ◽  
Author(s):  
B. Rita Alevriadou ◽  
Akshar Patel ◽  
Megan Noble ◽  
Sagnika Ghosh ◽  
Vishal M. Gohil ◽  
...  
Keyword(s):  
Cell Fate ◽  
Cell Function ◽  
Current Knowledge ◽  
Physiological Role ◽  
Mitochondrial Pathway ◽  
Dominant Negative ◽  
Multiple Organs ◽  
Calcium Uniporter ◽  
Intracellular Ca

Calcium (Ca2+) signaling is critical for cell function and cell survival. Mitochondria play a major role in regulating the intracellular Ca2+ concentration ([Ca2+]i). Mitochondrial Ca2+ uptake is an important determinant of cell fate and governs respiration, mitophagy/autophagy, and mitochondrial pathway of apoptosis. Mitochondrial Ca2+ uptake occurs via the mitochondrial Ca2+ uniporter (MCU) complex. This review summarizes the current knowledge on the function of MCU complex, regulation of MCU channel, and the role of MCU in Ca2+ homeostasis and human disease pathogenesis. The channel core consists of four MCU subunits and EMRE. Regulatory proteins that interact with them include mitochondrial Ca2+ uptake 1/2 (MICU1/2), MCU dominant negative beta subunit (MCUb), MCU regu­lator 1 (MCUR1) and solute carrier 25A23 (SLC25A23). In addition to these proteins, cardiolipin, a mito­chondrial mem­brane-specific phospholipid, has been shown to interact with the channel core. The dynamic interplay between the core and regu­latory proteins modulates MCU channel activity after sensing local changes in [Ca2+]i, reactive oxygen species, and other environmental factors. Here, we highlight the structural details of the human MCU heteromeric assemblies and their known roles in regulating mitochondrial Ca2+ homeostasis. MCU dysfunction has been shown to alter mitochondrial Ca2+ dynamics, in turn eliciting cell apoptosis. Changes in mitochondrial Ca2+ uptake have been implicated in pathological con­ditions af­fecting multiple organs, including the heart, skeletal muscle, and brain. However, our structural and functional knowledge of this vital protein complex remains incomplete and under­standing the precise role for MCU-mediated mito­chondrial Ca2+ signaling in disease requires further research ef­forts.

Regulation of ANP secretion by cardiac Na+/Ca2+ exchanger using a new controlled atrial model

2003 ◽  
Vol 284 (1) ◽  
pp. R31-R40
Author(s):  
Kyung Hwan Seul ◽  
Jeong Hee Han ◽  
Keum Yee Kang ◽  
Sung Zoo Kim ◽  
Suhn Hee Kim
Keyword(s):  
Stroke Volume ◽  
Atrial Natriuretic Peptide ◽  
Interstitial Fluid ◽  
Driving Forces ◽  
Physiological Role ◽  
Physical Factor ◽  
Systolic Volume ◽  
End Systolic Volume ◽  
Intracellular Ca

The myocardial interstitium is important in regulating cardiac function. Between the atrial lumen and the pericardial space are transmural pathways, and movement of interstitial fluid (ISF) through these pathways is one of the main driving forces regulating translocation of substances from the interstitium into the blood. To define how ISF translocation from the interstitial space into the luminal space is regulated by each component of atrial hemodynamics, we devised a new rabbit atrial model in which each physical parameter could be controlled independently. Using this system, we also defined the physiological role of the cardiac Na+/Ca2+ exchanger on secretion of atrial natriuretic peptide (ANP) by depletion of extracellular Na+ ([Na+]o). Increases in stroke volume and atrial end-systolic volume increased ISF translocation and ANP secretion. However, an increase in atrial rate did not influence ISF translocation but, rather, increased ANP secretion. Gradual depletion of [Na+]o caused gradual increases in ANP secretion and intracellular Ca2+([Ca2+]i), which were blocked in the presence of Ca2+-free buffer and Ni2+, but not in the presence of KB-R7943, diltiazem, mibefradil, caffeine, or monensin. Amiloride and its analog blocked an increase in ANP secretion but not an increase in [Ca2+]i by [Na+]o depletion. Therefore, we suggest that ANP secretion and ISF translocation may be differently controlled by each physical factor. These results also suggest that the increase in ANP secretion in response to [Na+]o depletion may involve inhibition of Na+/Ca2+ and Na+/H+ exchangers but not an increase in [Ca2+]i.

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