Effects of Osmolality on Paracellular Transport in MDCK II Cells

Abstract

Epithelia separate apical and basal compartments, and movement of substances via the paracellular pathway is regulated by tight junctions. Claudins are major constituents of tight junctions and involved in the regulation of tight junction permeability. On the other hand, the osmolality in the extracellular environment fluctuates in association with life activity. However, effects of osmotic changes on the permeaibility of claudins are poorly understood. Therefore, we investigated the effects of osmotic changes on the paracellular transport in MDCK II cells. Interestingly, apical hyposmolality decreased cation selectivity in the paracellular pathway gradually with time, and the elimination of the osmotic gradient promptly restored the cation selectivity. Apical hyposmolality also induced bleb formation at cell-cell contacts and changed the shape of cell-cell contacts from a jagged pattern to a slightly linear pattern. In claudin-2 knockout MDCK II cells, the decrease of cation selectivity, the bleb formation, nor the changes in the shape of cell-cell contacts was observed under the apical hyposmolality. Our findings in this study indicate that osmotic gradient between apical and basal sides is involved in the acute regulation of the cation selective property of claudin-2 channels.

Increased osmolality enhances the tight junction‐mediated barrier function in a cultured renal epithelial cell line

“…Osmotic alterations are associated with several human diseases, including brain edema, dry eye syndrome, inflammatory bowel disease, diabetes, and its complications (e.g., diabetic nephropathy) (Kawamata et al, 2007;Brocker et al, 2012;Johnson et al, 2014;Pasquel and Umpierrez, 2014;Umpierrez and Korytkowski, 2016). Experimental evidence has pointed out that changes in osmolarity (hypo or hyperosmolality) can affect epithelial transport (Ikari et al, 2013(Ikari et al, , 2015Tokuda et al, 2016). However, these studies are highly controversial: while some results indicate a significant disruption of the paracellular barrier (H€ ogman et al, 2002;Brown et al, 2004;Inokuchi et al, 2009), others show an enhancement of this barrier mediated by TJ after increasing the osmolarity (Ikari et al, 2012(Ikari et al, , 2013(Ikari et al, , 2015.…”

Rho Flares Repair Local Tight Junction Leaks

“…Epithelia in adult organisms also undergo high rates of cell division and cell extrusion, as epithelial tissues experience relatively high rates of cell turnover (Hooper, 1956;Macara et al, 2014). Indeed, other groups have reported short-lived, localized accumulation of F-actin and/or myosin II at junctions in Drosophila and cultured mammalian epithelial and endothelial cells during junction remodeling, indicating that Rho flare-like events may be a conserved process (Abu Taha et al, 2014;Pope and Harris, 2008;Razzell et al, 2014;Tokuda et al, 2016). Thus, we propose that the Rho flare mechanism described here may be broadly important for maintaining normal barrier function in developing and adult tissues.…”

Regulation of apical blebbing in the porcine epididymis

“…Molecular mechanisms involved in the release of these vesicles as well as conditions influencing the occurrence of blebbing (Tokuda et al. ; Zhang et al. ) have been studied in vitro .…”

“…Apical blebbing is a ubiquitous process used by cells during secretion, mitosis, migration and apoptosis, and characterizes some disease states (Charras et al 2008;Cocucci & Meldolesi, 2015;Shintaku & Maeno, 2016;Yamamoto et al 2016). Molecular mechanisms involved in the release of these vesicles as well as conditions influencing the occurrence of blebbing (Tokuda et al 2016;Zhang et al 2016) have been studied in vitro. Binding of extracellular ATP to P2RX7 initiates apical blebbing/membrane shedding in cultured cells (Baroni et al 2007;Pizzirani et al 2007;Cocucci et al 2009;Lee et al 2012;Cocucci & Meldolesi, 2015).…”