Hormonal regulation of Na+/K+-dependent ATPase activity and pump function in corneal endothelial cells

Potential Factors of Corneal Endothelial Cells for Progression in Children with Uveitis

Objective

To observe the morphological changes and abnormal structure of corneal endothelial cells in children with uveitis, to analyze the related factors affecting the morphological changes of corneal endothelial cells, and to explore the clinical application of a corneal endothelial microscope in children with uveitis.

Methods

The corneal endothelial cells of 70 patients with uveitis were photographed with the Topcon SP-3000 noncontact corneal endothelial microscope, and the corneal endothelial cell density (CD), average cell area (AVE), coefficient of variation of the cell area (CV), and percentage of hexagonal cells (PHC) were measured with the IMAGEnet system. Twenty-eight patients (56 eyes) with monocular uveitis were selected, with the affected eyes (28 eyes) as the experimental group and the contralateral healthy eyes (28 eyes) as the control group. The corneal endothelial cell parameters between the two groups were statistically analyzed. The parameters of corneal endothelial cells in 70 children with uveitis were compared, and the effects of the course of the disease, inflammatory cells in the anterior chamber, and posterior corneal deposition (KP) on the parameters of corneal endothelial cells were analyzed.

Results

There are four abnormal forms of the corneal endothelium in children with uveitis: enlarged cell area gap, irregular cell shape, blurred intercellular space, and cell loss. KP showed irregular high reflective white spots in the corneal endothelial microscope images, surrounded by dark areas, and existed in all the eyes with dusty KP found in slit lamp examination and a small number of eyes without obvious KP. Comparing the corneal endothelial cell parameters between the experimental group and the control group, it was found that the corneal endothelial CD and PHC of the former were lower than those of the latter, and the difference was statistically significant (P < 0.001 and P = 0.018, respectively). The AVE and CA of the former were higher than those of the latter (P = 0.013 and P = 0.046, respectively). The corneal endothelial cell density of the eyes with a course of the disease of more than 1 year was lower than that of the eyes with a course of the disease less than 1 year, the coefficient of variation of the corneal endothelial cell area of the eyes with KP was higher than that of the eyes without KP, and the difference was statistically significant (P = 0.003 and P = 0.030, respectively).

Conclusion

Corneal endothelial microscopy is one of the important methods for the detection of uveitis with high sensitivity. The change of morphological parameters of corneal endothelial cells is one of the important indexes to assist in the diagnosis of uveitis and can be further promoted in ophthalmological examination.

Effect of Rho-Associated Kinase Inhibitor and Mesenchymal Stem Cell-Derived Conditioned Medium on Corneal Endothelial Cell Senescence and Proliferation

This study aims to obtain sufficient corneal endothelial cells for regenerative application. We examined the combinatory effects of Rho-associated kinase (ROCK) inhibitor Y-27632 and mesenchymal stem cell-derived conditioned medium (MSC-CM) on the proliferation and senescence of rabbit corneal endothelial cells (rCECs). rCECs were cultured in a control medium, a control medium mixed with either Y-27632 or MSC-CM, and a combinatory medium containing Y-27632 and MSC-CM. Cells were analyzed for morphology, cell size, nuclei/cytoplasmic ratio, proliferation capacity and gene expression. rCECs cultured in a combinatory culture medium showed a higher passage number, cell proliferation, and low senescence. rCECs on collagen type I film showed high expression of tight junction. The cell proliferation marker Ki-67 was positively stained either in Y-27632 or MSC-CM-containing media. Genes related to cell proliferation resulted in negligible changes in MKI67, CIP2A, and PCNA in the combinatory medium, suggesting proliferative capacity was maintained. In contrast, all of these genes were significantly downregulated in the other groups. Senescence marker β-galactosidase-positive cells significantly decreased in either MSC-CM and/or Y-27632 mixed media. Senescence-related genes downregulated LMNB1 and MAP2K6, and upregulated MMP2. Cell cycle checkpoint genes such as CDC25C, CDCA2, and CIP2A did not vary in the combinatory medium but were significantly downregulated in either ROCK inhibitor or MSC-CM alone. These results imply the synergistic effect of combinatory culture medium on corneal endothelial cell proliferation and high cell number. This study supports high potential for translation to the development of human corneal endothelial tissue regeneration.

DR-region of Na+/K+-ATPase is a target to ameliorate hepatic insulin resistance in obese diabetic mice

Reduced hepatic Na⁺/K⁺-ATPase (NKA) activity and NKAα1 expression are engaged in the pathologies of metabolism diseases. The present study was designed to investigate the potential roles of NKAα1 in hepatic gluconeogenesis and glycogenesis in both hepatocytes and obese diabetic mice.

Methods: Insulin resistance was mimicked by glucosamine (GlcN) in either human hepatocellular carcinoma (HepG2) cells or primary mouse primary hepatocytes. Obese diabetic mice were induced by high-fat diet (HFD) feeding for 12 weeks.

Results: We found that both NKA activity and NKAα1 protein level were downregulated in GlcN-treated hepatocytes and in the livers of obese diabetic mice. Pharmacological inhibition of NKA with ouabain worsened, while activation of NKAα1 with an antibody against an extracellular DR region of NKAα1 subunit (DR-Ab) prevented GlcN-induced increase in gluconeogenesis and decrease in glycogenesis. Likewise, the above results were also corroborated by the opposite effects of genetic knockout/overexpression of NKAα1 on both gluconeogenesis and glycogenesis. In obese diabetic mice, hepatic activation or overexpression of NKAα1 stimulated the PI3K/Akt pathway to suppress hyperglycemia and improve insulin resistance. More importantly, loss of NKA activities in NKAα1^+/- mice was associated with more susceptibility to insulin resistance following HFD feeding.

Conclusions: Our findings suggest that NKAα1 is a physiological regulator of glucose homoeostasis and its DR-region is a novel target to treat hepatic insulin resistance.

Ex vivo quantitative analysis of human corneal stroma dehydration by near-infrared absorption spectroscopy

Corneal water content and hydrodynamics are critical indicators of eye health. In this work, a convenient method based on near-infrared absorption spectroscopy (NIRA) was presented to measure the relative water content of the corneal stroma ex vivo, which paves the way to measure corneal water content in vivo. The relative water content of fresh corneal stroma during dehydration under natural conditions (temperature, 25.8 ± 0.3°C; humidity, 7.2% ± 0.9%) was monitored in real time, and the characteristic time τ when the relative water content dropped to 90% of the fresh corneal stroma was 140.1 ± 30.6 s. Furthermore, the change in the relative water content over time was found to be linear with a dehydration rate of 0.071% per second, consistent with indirect optical coherence pachymetry but with superior reproducibility and precision. Provided that the NIRA spectrometer is changed to a reflection structure from the current transmission configuration, the NIRA method proposed in this work has great potential for in vivo measurement with the advantages of non-contact, high precision and low cost.

Glucocorticoid Treatment Leads to Aberrant Ion and Macromolecular Transport in Regenerating Zebrafish Fins

Long-term glucocorticoid administration in patients undergoing immunosuppressive and anti-inflammatory treatment is accompanied by impaired bone formation and increased fracture risk. Furthermore, glucocorticoid treatment can lead to impaired wound healing and altered cell metabolism. Recently, we showed that exposure of zebrafish to the glucocorticoid prednisolone during fin regeneration impacts negatively on the length, bone formation, and osteoblast function of the regenerate. The underlying cellular and molecular mechanisms of impairment, however, remain incompletely understood. In order to further elucidate the anti-regenerative effects of continued glucocorticoid exposure on fin tissues, we performed proteome profiling of fin regenerates undergoing prednisolone treatment, in addition to profiling of homeostatic fin tissue and fins undergoing undisturbed regeneration. By using LC-MS (liquid chromatography-mass spectrometry) we identified more than 6,000 proteins across all tissue samples. In agreement with previous reports, fin amputation induces changes in chromatin structure and extracellular matrix (ECM) composition within the tissue. Notably, prednisolone treatment leads to impaired expression of selected ECM components in the fin regenerate. Moreover, the function of ion transporting ATPases and other proteins involved in macromolecule and vesicular transport mechanisms of the cell appears to be altered by prednisolone treatment. In particular, acidification of membrane-enclosed organelles such as lysosomes is inhibited. Taken together, our data indicate that continued synthetic glucocorticoid exposure in zebrafish deteriorates cellular trafficking processes in the regenerating fin, which interferes with appropriate tissue restoration upon injury.

DR region of Na+-K+-ATPase is a new target to protect heart against oxidative injury

Previous studies have shown that the activity and expression of Na⁺/K⁺-ATPase (NKA) are down-regulated in the failing hearts, and that an antibody against the DR-region of NKA (DR-Ab) can stimulate its activity. The present study was designed to investigate the beneficial effects of this antibody against cardiac injury and the underlying mechanisms. We found that DR-Ab improved cardiac function, alleviated cardiac hypertrophy and reduced oxidative stress in isoproterenol-treated mice. In AC16 human cardiomyocytes, DR-Ab increased cell viability and attenuated apoptosis under oxidative stress. Corresponding to the observation of reduced NKA activity, NKA abundance on plasma membrane was lowered during oxidative stress. Suppressed activity of protein phosphatase 2 A (PP2A) was responsible for the loss of membrane NKA due to the increased phosphorylation of key serine residues that trigger endocytosis. Incubation with DR-Ab restored PP2A activity and stabilized NKA expression on the plasma membrane. Inhibitors of PP2A abolished the protective effect of DR-Ab against oxidative stress. In summary, our data indicate that loss of membrane NKA may contribute to cardiac pathologies in heart failure. DR-Ab, by stabilizing membrane NKA, protects cardiomyocytes against oxidative injury and improves cardiac function in the failing hearts, suggesting a novel approach to treat heart failure.

Biomechanics and structure of the cornea: implications and association with corneal disorders

Recent studies have shown that alterations in corneal biomechanical properties are associated with corneal pathologies, particularly corneal ectasia. Moreover, these alterations may have implications with regard to the outcomes of therapeutic modalities and corneal refractive surgeries. We address corneal anatomy and its relevance to corneal biomechanical characteristics, as well as ocular and systemic conditions associated with changes in corneal biomechanics.

Stemness characteristics of human corneal endothelial cells cultured in various media

PURPOSE

To investigate stemness characteristics of human corneal endothelial cells (HCECs) cultured in various media.

METHODS

Human corneal endothelial cells were isolated using a sphere-forming assay. Cells were allowed to attach to the bottom of culture plates and were cultured in different media designated as medium A (Opti-MEM I with 8% fetal bovine serum), medium B (DMEM/F12 with B27 supplement), medium E (DMEM/F12 with epidermal growth factor [EGF]), and medium BE (DMEM/F12 with B27 supplement and EGF), respectively. Cell morphology was evaluated with an phase-contrast inverted microscope. Immunofluorescence staining and western blotting of nestin, octamer-binding transcription factor (OCT3/4), glial fibrillary acidic protein (GFAP), zonula occludens-1 (ZO-1), collagen VIII alpha2, and Na-K ATPase was performed. Cell proliferation was assessed with a cell counting kit-8 assay.

RESULTS

A few cultured cells stained with nestin. The cells cultured in medium A expressed high levels of GFAP, OCT3/4, and nestin, and higher levels of ZO-1 were expressed in the cells cultured in medium A and medium B compared with cells cultured in the other media. The cells cultured in medium A assumed a fibroblast-like shape, whereas the cells cultured in medium B and medium BE appeared as mosaics. Cell proliferation was highest in medium A compared with those cultured in the other media.

CONCLUSIONS

Cultured HCECs expressed stem cell markers, including nestin, OCT3/4, and GFAP. The expression of stem cell markers differed according to the culture media and associated proliferation rate.

Cerebral Oedema, Blood-Brain Barrier Breakdown and the Decrease in Na(+),K(+)-ATPase Activity in the Cerebral Cortex and Hippocampus are Prevented by Dexamethasone in an Animal Model of Maple Syrup Urine Disease

Maple syrup urine disease (MSUD) is a rare metabolic disorder associated with acute and chronic brain dysfunction. This condition has been shown to lead to macroscopic cerebral alterations that are visible on imaging studies. Cerebral oedema is widely considered to be detrimental for MSUD patients; however, the mechanisms involved are still poorly understood. Therefore, we investigated whether acute administration of branched-chain amino acids (BCAA) causes cerebral oedema, modifies the Na(+),K(+)-ATPase activity, affects the permeability of the blood-brain barrier (BBB) and alters the levels of cytokines in the hippocampus and cerebral cortex of 10-day-old rats. Additionally, we investigated the influence of concomitant administration of dexamethasone on the alterations caused by BCAA. Our results showed that the animals submitted to the model of MSUD exhibited an increase in the brain water content, both in the cerebral cortex and in the hippocampus. By investigating the mechanism of cerebral oedema, we discovered an association between H-BCAA and the Na(+),K(+)-ATPase activity and the permeability of the BBB to small molecules. Moreover, the H-BCAA administration increases Il-1β, IL-6 and TNF-α levels in the hippocampus and cerebral cortex, whereas IL-10 levels were decreased in the hippocampus. Interestingly, we showed that the administration of dexamethasone successfully reduced cerebral oedema, preventing the inhibition of Na(+),K(+)-ATPase activity, BBB breakdown and the increase in the cytokines levels. In conclusion, these findings suggest that dexamethasone can improve the acute cerebral oedema and brain injury associated with high levels of BCAA, either through a direct effect on brain capillary Na(+),K(+)-ATPase or through a generalized effect on the permeability of the BBB to all compounds.

Endothelial graft failure after contralateral autologous corneal transplantation

PURPOSE

To report on outcomes after contralateral autologous penetrating keratoplasty (APK).

DESIGN

Case series.

PATIENT POPULATION

Five patients who received a contralateral APK and a simultaneous allogeneic penetrating keratoplasty in the donor eye at the Bascom Palmer Eye Institute and the Miami Veterans Affairs Hospital.

RESULTS

The median patient age at the time of surgery in our 5 patients was 67 years (range, 58-88 years); 4 patients were male and 1 female, and 1 patient was white and 4 were black. The surgery was uneventful in all cases, and no operative or immediate postoperative complications occurred in either eye. Follow-up time ranged from 18 to 54 months (mean, 35 months; median, 34 months). During this time, 4 of the autologous grafts failed because of endothelial attenuation. Identified risk factors for failure in the autologous eyes included the presence of a glaucoma tube (5/5), previous graft failure (4/5), and anterior synechiae (2/5).

CONCLUSIONS

This study is the first to describe graft failure because of slow endothelial attenuation after APK. This study underscores the importance of nonimmunologic factors in endothelial cell loss after corneal transplant surgery and highlights the need for further research to understand and modulate endothelial loss.

Na(+),K (+)-ATPase as a docking station: protein-protein complexes of the Na(+),K (+)-ATPase

The Na(+),K(+)-ATPase, or sodium pump, is well known for its role in ion transport across the plasma membrane of animal cells. It carries out the transport of Na(+) ions out of the cell and of K(+) ions into the cell and thus maintains electrolyte and fluid balance. In addition to the fundamental ion-pumping function of the Na(+),K(+)-ATPase, recent work has suggested additional roles for Na(+),K(+)-ATPase in signal transduction and biomembrane structure. Several signaling pathways have been found to involve Na(+),K(+)-ATPase, which serves as a docking station for a fast-growing number of protein interaction partners. In this review, we focus on Na(+),K(+)-ATPase as a signal transducer, but also briefly discuss other Na(+),K(+)-ATPase protein-protein interactions, providing a comprehensive overview of the diverse signaling functions ascribed to this well-known enzyme.