Effect of Alpha-Glucosyl-Hesperidin Consumption on Lens Sclerosis and Presbyopia

Presbyopia is characterized by a decline in the ability to accommodate the lens. The most commonly accepted theory for the onset of presbyopia is an age-related increase in the stiffness of the lens. However, the cause of lens sclerosis remains unclear. With age, water microcirculation in the lens could change because of an increase in intracellular pressure. In the lens, the intracellular pressure is controlled by the Transient Receptor Potential Vanilloid (TRPV) 1 and TRPV4 feedback pathways. In this study, we tried to elucidate that administration of α-glucosyl-hesperidin (G-Hsd), previously reported to prevent nuclear cataract formation, affects lens elasticity and the distribution of TRPV channels and Aquaporin (AQP) channels to meet the requirement of intracellular pressure. As a result, the mouse control lens was significantly toughened compared to both the 1% and 2% G-Hsd mouse lens treatments. The anti-oxidant levels in the lens and plasma decreased with age; however, this decrease could be nullified with either 1% or 2% G-Hsd treatment in a concentration- and exposure time-dependent manner. Moreover, G-Hsd treatment affected the TRPV4 distribution, but not TRPV1, AQP0, and AQP5, in the peripheral area and could maintain intracellular pressure. These findings suggest that G-Hsd has great potential as a compound to prevent presbyopia and/or cataract formation.

Myosin II and Arp2/3 crosstalk governs intracellular hydraulic pressure and lamellipodia formation

Human fibroblasts can switch between lamellipodia-dependent and -independent migration mechanisms on 2D surfaces and in 3D matrices. RhoA GTPase activity governs the switch from low-pressure lamellipodia to high-pressure lobopodia in response to the physical structure of the 3D matrix. Inhibiting actomyosin contractility in these cells reduces intracellular pressure and reverts lobopodia to lamellipodial protrusions via an unknown mechanism. To test the hypothesis that high pressure physically prevents lamellipodia formation, we manipulated pressure by activating RhoA or changing the osmolarity of the extracellular environment and imaged cell protrusions. We find RhoA activity inhibits Rac1-mediated lamellipodia formation through two distinct pathways. First, RhoA boosts intracellular pressure by increasing actomyosin contractility and water influx but acts upstream of Rac1 to inhibit lamellipodia formation. Increasing osmotic pressure revealed a second RhoA pathway which acts through non-muscle myosin II (NMII) to disrupt lamellipodia downstream of Rac1 and elevate pressure. Interestingly, Arp2/3 inhibition triggered a NMII-dependent increase in intracellular pressure, along with lamellipodia disruption. Together, these results suggest that actomyosin contractility and water influx are coordinated to increase intracellular pressure, and RhoA signaling can inhibit lamellipodia formation via two distinct pathways in high-pressure cells. [Media: see text] [Media: see text] [Media: see text]

The mechanism of osmotically induced sealing of cardiac t tubules

This study provides new insights into how t-tubular membranes respond to osmotic forces. In particular, the data show that osmotically induced sealing of cardiac t tubules is a threshold phenomenon initiated by detachment of t-tubular membrane from the underlying cytoskeleton. The findings are consistent with the hypothesis that final sealing of t tubules is driven by negative hydrostatic intracellular pressure coincident with cell shrinking.

Influence of saltwater intake on the health of dairy cattle

Water is an element extremely important, essential for life, and necessary to maintain some factors such as intracellular pressure, assist digestive processes, carry nutrients, eliminate toxins through urine and allow the thermal balance of living things. However, it is a scarce element as the national water resources policy in Brazil advocates. In recent years water has become one of the biggest global problems due to lack and quality. The objective of this study was to evaluate the influence of saline intake on the health of dairy cattle. The actions consisted of periodic visits to a rural property located in the city of Pesqueira, Agreste Pernambucano - Brazil, whose main economic activity is milk production and cheese making. The herd has milk aptitude and consists of 182 animals. Samples of desalination tailings water that were supplied for quench the animals were collected. Blood samples from the cattle were collected and sent for hematological exams. The results showed alterations of some physicochemical parameters of water and high serum levels of chloride and sodium in cattle. The continuous intake of wastewater from the desalination process for the quench of dairy cattle alters the serological and physiological patterns of these animals. Further studies must be conducted on dairy products regarding their quality and health impact.

Inhibition of cell membrane ingression at the division site by cell wall in fission yeast

Eukaryotic cells assemble an actomyosin ring during cytokinesis to function as a force-generating machine to drive membrane invagination, and to counteract the intracellular pressure and the cell surface tension. It is unclear whether additional factors such as the extracellular matrix (cell wall in yeasts and fungi) affect the actomyosin ring contraction. While studying the fission yeast β-glucan synthase mutant cps1-191, which is defective in division septum synthesis and actomyosin ring contraction, we found that significantly weakening of the extracellular glycan matrix caused the spheroplasts to divide at the non-permissive condition. This division was dependent on a functional actomyosin ring and vesicular trafficking, but independent of normal septum synthesis. cps1-191 cells with weakened extracellular glycan matrix divide non-medially with a much slower ring contraction rate compared to wild type cells under similar conditions, which we term as cytofission. Interestingly, the high turgor pressure appears to play minimal roles in inhibiting ring contraction in cps1-191 mutants as decreasing the turgor pressure alone does not enable cytofission. We propose that during cytokinesis, the extracellular glycan matrix restricts actomyosin ring contraction and membrane ingression, and remodeling of the extracellular components through division septum synthesis relieves the inhibition and facilitates actomyosin ring contraction.

A unified role for membrane-cortex detachment during cell protrusion initiation

Cell morphogenesis employs a diversity of membrane protrusions. They are discriminated by differences in force generation. Actin polymerization is the best studied mechanism of force generation, but growing interest in how variable molecular conditions and microenvironments alter morphogenesis has revealed other mechanisms, including intracellular pressure. Here, we show that local depletion of membrane cortex links is an essential step in the initiation of both pressure-based and actin-based protrusions. This observation challenges the quarter-century old Brownian ratchet model of actin-driven membrane protrusion, which requires an optimal balance of actin filament growth and membrane tethering. An updated model confirms membrane-filament detachment is necessary to activate the ratchet mechanism. These findings unify the regulation of different protrusion types, explaining how cells generate robust yet flexible strategies of morphogenesis.

Myosin II governs intracellular pressure and traction by distinct tropomyosin-dependent mechanisms

Two-dimensional (2D) substrate rigidity promotes myosin II activity to increase traction force in a process negatively regulated by tropomyosin (Tpm) 2.1. We recently discovered that actomyosin contractility can increase intracellular pressure and switch tumor cells from low-pressure lamellipodia to high-pressure lobopodial protrusions during three-dimensional (3D) migration. However, it remains unclear whether these myosin II–generated cellular forces are produced simultaneously, and by the same molecular machinery. Here we identify Tpm 1.6 as a positive regulator of intracellular pressure and confirm that Tpm 2.1 is a negative regulator of traction force. We find that Tpm 1.6 and 2.1 can control intracellular pressure and traction independently, suggesting these myosin II–dependent forces are generated by distinct mechanisms. Further, these tropomyosin-regulated mechanisms can be integrated to control complex cell behaviors on 2D and in 3D environments.

Time-resolved ultrastructure of the cortical actin cytoskeleton in dynamic membrane blebs

Membrane blebbing accompanies various cellular processes, including cytokinesis, apoptosis, and cell migration, especially invasive migration of cancer cells. Blebs are extruded by intracellular pressure and are initially cytoskeleton-free, but they subsequently assemble the cytoskeleton, which can drive bleb retraction. Despite increasing appreciation of physiological significance of blebbing, the molecular and, especially, structural mechanisms controlling bleb dynamics are incompletely understood. We induced membrane blebbing in human HT1080 fibrosarcoma cells by inhibiting the Arp2/3 complex. Using correlative platinum replica electron microscopy, we characterize cytoskeletal architecture of the actin cortex in cells during initiation of blebbing and in blebs at different stages of their expansion–retraction cycle. The transition to blebbing in these conditions occurred through an intermediate filopodial stage, whereas bleb initiation was biased toward filopodial bases, where the cytoskeleton exhibited local weaknesses. Different stages of the bleb life cycle (expansion, pausing, and retraction) are characterized by specific features of cytoskeleton organization that provide implications about mechanisms of cytoskeleton assembly and bleb retraction.

Large Cytoplasmic Vacuoles within Notochordal Nucleus Pulposus Cells: A Possible Regulator of Intracellular Pressure That Shapes the Cytoskeleton and Controls Proliferation

Degeneration of the intervertebral disc, which is closely associated with the loss of vacuolated notochordal nucleus pulposus cells (NNPC), remains a major cause of lower-back pain and motor deficiency. Being the most defining characteristic of NNPC, large cytoplasmic vacuoles not only modulate the cytoskeleton and shape cell morphology but they also respond to the disc microenvironment and regulate the biological behavior of vacuolated cells as a potent reporter of the histocytological changes that occur at the beginning of disc aging and degeneration. Here we hypothesize a model in which large cytoplasmic vacuoles primarily function to maintain a reasonable intracellular pressure (Pv) that facilitates NNPC in resisting the extracellular mechanical loading (Pe), part of which is absorbed by the extracellular matrix (Pm), forming the equation Pe = Pm + Pv. By mimicking a situation of contact-induced growth inhibition, the crowded cytoplasmic vacuoles slow down the proliferation of NNPC and restrain the generation of nonvacuolated chondrocytic nucleus pulposus cells (CNPC), whereas increased mechanical loading (↑Pe) alters cytoskeletons and breaches cytoplasmic vacuoles, which in turn weakens the vacuoles-mediated proliferation check, increases the generation of CNPC that accumulates fibrocartilaginous matrix, and rebalances the increased loading with elevated Pm (↑Pm) and lowered Pv (↓Pv), equating to ↑Pe = ↑Pm + ↓Pv. By depicting the biological function and the disappearance of the cytoplasmic vacuoles, our model highlights a mechanical exhaustion of the notochordal cell resources, which might help to elucidate the histocytological changes that initiate disc aging and degeneration.