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Biophysical Journal May 2022Caveola membrane structures harbor mechanosensitive chloride channels (MCCs; including chloride channel 2, chloride channel 3, and SWELL1, also known as LRRC8A) that...
Caveola membrane structures harbor mechanosensitive chloride channels (MCCs; including chloride channel 2, chloride channel 3, and SWELL1, also known as LRRC8A) that form a swelling-activated chloride current (I) and play an important role in cell volume regulation and mechanoelectrical signal transduction. However, the role of the muscle-specific caveolar scaffolding protein caveolin-3 (Cav3) in regulation of MCC expression, activity, and contribution to membrane integrity in response to mechanical stress remains unclear. Here we showed that Cav3-transfected (Cav3-positive) HEK293 cells were significantly resistant to extreme (<20 milliosmole) hypotonic swelling compared with native (Cav3-negative) HEK293 cells; the percentage of cells with membrane damage decreased from 45% in Cav3-negative cells to 17% in Cav3-positive cells (p < 0.05). This mechanoprotection was significantly reduced (p < 0.05) when cells were exposed to the I-selective inhibitor 4-[(2-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]butanoic acid (10 μM). These results were recapitulated in isolated mouse ventricular myocytes, where the percentage of cardiomyocytes with membrane damage increased from 47% in control cells to 78% in 4-[(2-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]butanoic acid-treated cells (p < 0.05). A higher resistance to hypotonic swelling in Cav3-positive HEK293 cells was accompanied by a significant twofold increase of I current density and SWELL1 protein expression, whereas ClC-2/3 protein levels remained unchanged. Förster resonance energy transfer analysis showed a less than 10-nm membrane and intracellular association between Cav3 and SWELL1. Cav3/SWELL1 membrane Förster resonance energy transfer efficiency was halved in mild (220 milliosmole) hypotonic solution as well as after disruption of caveola structures via cholesterol depletion by 1-h treatment with 10 mM methyl-β-cyclodextrin. A close association between Cav3 and SWELL1 was confirmed by co-immunoprecipitation analysis. Our findings indicate that, in the MCCs tested, SWELL1 abundance and activity are regulated by Cav3 and that their association relies on membrane tension and caveola integrity. This study highlights the mechanoprotective role of Cav3, which is facilitated by complimentary SWELL1 expression and activity.
Topics: Animals; Butyric Acid; Caveolin 3; Cell Size; Chloride Channels; Chlorides; HEK293 Cells; Humans; Membrane Proteins; Mice
PubMed: 35378081
DOI: 10.1016/j.bpj.2022.04.001 -
PLoS Biology Apr 2017Diffusion functional MRI (DfMRI) reveals neuronal activation even when neurovascular coupling is abolished, contrary to blood oxygenation level-dependent (BOLD)...
Diffusion functional MRI (DfMRI) reveals neuronal activation even when neurovascular coupling is abolished, contrary to blood oxygenation level-dependent (BOLD) functional MRI (fMRI). Here, we show that the water apparent diffusion coefficient (ADC) derived from DfMRI increased in specific rat brain regions under anesthetic conditions, reflecting the decreased neuronal activity observed with local field potentials (LFPs), especially in regions involved in wakefulness. In contrast, BOLD signals showed nonspecific changes, reflecting systemic effects of the anesthesia on overall brain hemodynamics status. Electrical stimulation of the central medial thalamus nucleus (CM) exhibiting this anesthesia-induced ADC increase led the animals to transiently wake up. Infusion in the CM of furosemide, a specific neuronal swelling blocker, led the ADC to increase further locally, although LFP activity remained unchanged, and increased the current threshold awakening the animals under CM electrical stimulation. Oppositely, induction of cell swelling in the CM through infusion of a hypotonic solution (-80 milliosmole [mOsm] artificial cerebrospinal fluid [aCSF]) led to a local ADC decrease and a lower current threshold to wake up the animals. Strikingly, the local ADC changes produced by blocking or enhancing cell swelling in the CM were also mirrored remotely in areas functionally connected to the CM, such as the cingulate and somatosensory cortex. Together, those results strongly suggest that neuronal swelling is a significant mechanism underlying DfMRI.
Topics: Action Potentials; Anesthesia, General; Animals; Brain; Brain Mapping; Cerebrovascular Circulation; Diffusion; Diffusion Magnetic Resonance Imaging; Dose-Response Relationship, Drug; Electric Stimulation; Isoflurane; Male; Medetomidine; Oxygen; Rats, Wistar; Wakefulness; Water
PubMed: 28406906
DOI: 10.1371/journal.pbio.2001494 -
Canadian Journal of Psychiatry. Revue... Jun 2014Despite being a common and potentially serious condition, nephrogenic diabetes insipidus (NDI) remains poorly understood in older lithium users. Our main objective was...
OBJECTIVE
Despite being a common and potentially serious condition, nephrogenic diabetes insipidus (NDI) remains poorly understood in older lithium users. Our main objective was to compare the prevalence of NDI symptoms and decreased urine osmolality ([UOsm] < 300 milli-Osmoles [mOsm/kg]) among geriatric and adult lithium users. We also assessed NDI symptoms, serum sodium (Na+), and urine specific gravity (USG) as possible surrogate measures of decreased UOsm, and ascertained whether potential etiologic factors independently correlated with decreased UOsm.
METHOD
This was a cross-sectional study of 100 consecutive outpatients treated with lithium from 6 tertiary care clinics, of which 45 were geriatric (aged 65 years and older) and 55 adult (aged 18 to 64 years). Patients completed a symptom questionnaire and underwent laboratory tests, including UOsm, serum Na+, and USG.
RESULTS
Geriatric and adult lithium users had similar rates of decreased UOsm (12.5%, compared with 17.9%, P = 0.74), but geriatric patients reported less symptoms (P < 0.05). Although UOsm did not correlate with symptoms or current serum Na+, USG of less than 1.010 was suggestive of UOsm of less than 300 mOsm/kg. Age, lithium duration, and serum lithium level were independently associated with UOsm.
CONCLUSIONS
The prevalence of decreased UOsm is similar in geriatric and adult lithium users, but older patients are less likely to report urinary and thirst symptoms. Although subjective symptoms do not correlate with UOsm, USG may be a cost-efficient clinical surrogate measure for UOsm. We suggest clinicians increase their vigilance for decreased UOsm, especially in lithium users with advanced age, longer duration of lithium exposure, and higher lithium levels. This may potentially prevent lithium intoxication, falls, hypernatremic events, and renal dysfunction.
Topics: Adolescent; Adult; Age Factors; Aged; Bipolar Disorder; Cross-Sectional Studies; Depressive Disorder, Major; Diabetes Insipidus, Nephrogenic; Dose-Response Relationship, Drug; Female; Humans; Lithium Compounds; Male; Middle Aged; Osmolar Concentration; Reference Values; Sodium; Specific Gravity; Young Adult
PubMed: 25007407
DOI: 10.1177/070674371405900606 -
International Journal of Ophthalmology 2013To compare the effects of first and second generation silicone hydrogel (SiH) contact lens wear on tear film osmolarity.
AIM
To compare the effects of first and second generation silicone hydrogel (SiH) contact lens wear on tear film osmolarity.
METHODS
The healthy subjects who have never used contact lenses before were enrolled in the study. Tear film osmolarity values of 16 eyes (group 1) who wore first generation SiH contact lenses were compared with those of 18 eyes (group 2) who wore second generation SiH contact lenses after three months follow-up.
RESULTS
Before contact lens wear, tear film osmolarity of groups 1 and 2 were 305.02±49.08 milliosmole (mOsm) and 284.66±30.18mOsm, respectively. After three months of contact lens wear, osmolarity values were found 317.74±60.23mOsm in group 1 and 298.40±37.77mOsm in group 2. Although osmolarity values for both groups of SiH contact lens wear after three months periods were slightly higher than before the contact lens wear, the difference was not statistically significant.
CONCLUSION
Contact lens wear may cause evaporation from the tear film and can increase tear film osmolarity leading to symptoms of dry eye disease. In the current study, there is a tendency to increase tear film osmolarity for both groups of SiH contact lens wear, but the difference is not statistically significant.
PubMed: 24195046
DOI: 10.3980/j.issn.2222-3959.2013.05.22 -
American Journal of Physiology. Renal... Feb 2024The urine concentration impairment responsible for hyposthenuria in sickle cell nephropathy is currently thought to be a consequence of renal medulla lesions, which lead... (Observational Study)
Observational Study
The urine concentration impairment responsible for hyposthenuria in sickle cell nephropathy is currently thought to be a consequence of renal medulla lesions, which lead to nephrogenic diabetes insipidus. The objective of the present study was to investigate the mechanism of hyposthenuria in patients with sickle cell anemia. We performed an observational study of patients with homozygous SS sickle cell anemia and data available on the fasting plasma antidiuretic hormone (ADH) concentration. A total of 55 patients were analyzed. The fasting plasma ADH values ranged from 1.2 to 15.4 pg/mL, and 82% of the patients had elevated ADH values and low fasting urine osmolality (<505 mosmol/kgHO). Plasma ADH was positively associated with plasma tonicity and natremia ( < 0.001). None of the patients experienced polyuria and fasting free water clearance was negative in all cases, thus, ruling out nephrogenic diabetes insipidus. The tertile groups did not differ with regard to fasting urine osmolality, plasma renin level, mGFR, or several hemolysis biomarkers. The negative fasting free water clearance in all cases and the strong association between 24-h osmolal clearance and 24-h diuresis favors the diagnosis of osmotic diuresis due to an impaired medullary gradient, rather than lesions to collecting tubule. The urine concentration impairment in sickle cell anemia is an osmotic diuresis related to an impaired renal medullary gradient leading to an ADH plateau effect. The fasting plasma ADH was high in the context of a basic state of close-to-maximal urine concentration probably driven by short nephrons maintaining a cortex-outer medullary gradient (about 400 milliosmoles). The patients had a low daily osmoles intake without evidence of thirst dysregulation so no one experienced polyuria.
Topics: Humans; Diabetes Insipidus, Nephrogenic; Polyuria; Diuresis; Osmolar Concentration; Antidiuretic Agents; Water; Anemia, Sickle Cell; Diabetes Insipidus; Diabetes Mellitus
PubMed: 38059298
DOI: 10.1152/ajprenal.00313.2023 -
Proceedings of the National Academy of... Apr 2006Aquaporin-2 (AQP2) is the predominant vasopressin-regulated water channel in kidney connecting tubule (CNT) and collecting duct (CD) and is essential for renal...
Aquaporin-2 (AQP2) is the predominant vasopressin-regulated water channel in kidney connecting tubule (CNT) and collecting duct (CD) and is essential for renal regulation of body water balance. However, the relative role of AQP2 to urinary concentration in the CNT and CD segments is unknown. To examine this directly, transgenic mice expressing AQP2 selectively in CNT but lacking AQP2 expression in CD (AQP2-CD-KO) and mice lacking AQP2 globally (AQP2-total-KO) were generated by exploiting the Cre/loxP technology. LoxP sites were inserted into AQP2 introns 2 and 3, and transgenic mice were bred with strains expressing Cre recombinase under the control of CD-specific Hoxb7- or global EIIa promoter. Mice lacking AQP2 globally died postnatally (days 5-12). AQP2-CD-KO mice were viable to adulthood and showed decreased body weight, 10-fold increased urine production (0.96 +/- 0.11 vs. 0.10 +/- 0.01 ml/g of body weight), and decreased urinary osmolality (170 +/- 19 vs. 1,630 +/- 135 milliosmoles/kg of H(2)O). Immunohistochemical staining of AQP2-CD-KO kidneys (n = 12) revealed sustained, strong AQP2 expression in CNT cells, whereas >95% of CD principal cells were completely AQP2-negative. Water deprivation for 3 hours caused only marginal decreased urine output (87 +/- 7% of levels when mice had free water access; P = 0.04) with no change in urine osmolality, revealing an absence of compensatory mechanisms. These results demonstrate that AQP2 in CNT is sufficient for postnatal survival and that AQP2 in CD is essential for regulation of body water balance and cannot be compensated for by other mechanisms.
Topics: Animals; Aquaporin 2; Gene Deletion; Immunohistochemistry; Kidney Tubules, Collecting; Mice; Mice, Knockout; Models, Molecular; Protein Conformation; Recombination, Genetic; Urine; Water-Electrolyte Balance
PubMed: 16581908
DOI: 10.1073/pnas.0511324103 -
Plant Physiology Mar 1991Sucrose uptake was studied in isolated, immature pea cotyledons (Pisum sativum L. cv Marzia) in relation to their developmental stage. During the developmental period...
Sucrose uptake was studied in isolated, immature pea cotyledons (Pisum sativum L. cv Marzia) in relation to their developmental stage. During the developmental period examined the water content of the cotyledons decreased from approximately 80% "stage 1" to approximately 55% "stage 2". When assayed in an isotonic medium (400 osmoles per cubic meter) the influx capacity per gram fresh weight for sucrose was almost constant during this developmental period. The influx could be analyzed into a saturable component (K(m) approximately 9 moles per cubic meter; V(max) approximately 150 nanomoles per minute per gram fresh weight) and an unsaturable component (k(i) approximately 0.5 nanomoles per minute per gram fresh weight [per mole per cubic meter]). Incubation in a hypotonic medium reduced the sucrose influx in stage 1 cotyledons, up to 80% reduction at 0 milliosmole (medium without mannitol), but had no effect on sucrose uptake by stage 2 cotyledons. Reduced uptake in a hypotonic medium (100 osmoles per cubic meter) could be attributed to a lowering of the V(max) from 150 to 36 nanomoles per minute per gram fresh weight. During incubation of stage 1 cotyledons and stage 2-cotyledons in a hypotonic medium (200 osmoles per cubic meter) their volume increased by 16% and 5.6%, respectively, while the calculated turgor pressure increased from 0.2 to 0.6 megapascal for cotyledons of both developmental stages. Reduced sucrose influx in hypotonic medium, therefore, seems to be related to cell swelling (membrane stretching) rather than to increased turgor pressure.
PubMed: 16668061
DOI: 10.1104/pp.95.3.832 -
Journal of Neurology, Neurosurgery, and... Feb 1971A total of 132 urine specimens were obtained from 17 depressed patients and 18 controls under conditions of mild water deprivation. Mean values of milliosmoles of solute...
A total of 132 urine specimens were obtained from 17 depressed patients and 18 controls under conditions of mild water deprivation. Mean values of milliosmoles of solute and millilitres of urine excreted per hour were obtained for each subject. The depressed patients excreted significantly less solute than the control group per unit volume of urine. There was no significant difference between the solute excretion rates of depressed patients and those who had recently recovered from depression-though the trend was towards normality. The significance of these results is discussed in relation to studies on body fluids and electrolytes and the role of ADH and aldosterone in affective disorders.
Topics: Adult; Anxiety Disorders; Body Fluids; Depression; Electroconvulsive Therapy; Humans; Middle Aged; Osmolar Concentration; Schizophrenia; Water Deprivation; Water-Electrolyte Balance
PubMed: 5551692
DOI: 10.1136/jnnp.34.1.30