Permeability properties of the teleost gill epithelium under ion-poor conditions

Abstract

Permeability properties of the goldfish gill epithelium were examined in vivo and in vitro following exposure to ion-poor water (IPW) conditions. In gill tissue of IPW-acclimated goldfish, transcript abundance of tight junction (TJ) proteins occludin, claudin-b, -d, -e, -h, -7, and -8d increased, whereas ZO-1 and claudin 12 mRNA decreased and claudin-c was unaltered. In association with these changes, TJ depth increased among gill pavement cells (PVCs) and gill PVCs and mitochondria-rich cells (MRCs). PVC and MRC gill cell fractions were isolated using Percoll. Transcripts encoding for occludin, claudin-b, -c, -d, -e, -h, -7, -8d, -12, and ZO-1 were present in both fractions. After IPW acclimation, occludin, claudin-b and -e, and ZO-1 mRNA abundance increased in both fractions. In contrast, claudin-8d mRNA abundance increased in PVCs only while claudin-h decreased in MRCs. Gill permeability was examined using primary cultured goldfish PVC epithelia supplemented with serum derived from IPW-acclimated goldfish. IPW serum supplementation increased transepithelial resistance, reduced [(3)H]PEG-4000 permeability, and enhanced epithelial integrity during in vitro IPW exposure. IPW serum increased mRNA abundance of occludin, claudin-8d and -e in vitro. Using small interfering RNA, we found that occludin abundance was decreased in cultured gill epithelia, resulting in an increase in [(3)H]PEG-4000 flux. As occludin increased in the gills of IPW-acclimated fish as well as cultured gill epithelia exposed to IPW serum, results suggest that occludin is a barrier-forming TJ protein in fish gill epithelia. These studies support the idea that TJ proteins play an important role in regulating gill permeability in IPW.

Dietary tryptophan modulates intestinal immune response, barrier function, antioxidant status and gene expression of TOR and Nrf2 in young grass carp (Ctenopharyngodon idella)

“…Several lines of evidence support a barrier-forming role for ZO-1, occludin, claudin-b, -c and -3 in fish [77,78], whereas claudin-12 and -15 in rats seem to possess pore-forming characteristics [79,80]. Moreover, the up-regulation of ZO-1 and occludin [81] and down-regulation of claudin-15 [82] attenuated the loss of the Fig.…”

Dietary choline regulates antibacterial activity, inflammatory response and barrier function in the gills of grass carp (Ctenopharyngodon idella)

“…Moreover, ZO-1, occludin, claudin-b, claudin-c, claudin-3 are the barrier-forming TJ proteins in fish [26], whereas claudin-12 and claudin-15 in rats seem to possess pore-forming characteristics [13]. In this study, dietary choline supplementation significantly up-regulated the ZO-1, occludin, claudin-b, claudin-c, claudin-3 mRNA levels in the gills of grass carp, implying that choline might improve the barrier function of fish gill.…”

“…A growing number of researches indicated that the gill epithelium barrier is partly regulated by tight junctions (TJ) [25]. Moreover, in fish gill, TJ complex was composed by transmembrane (such as Occludin and Claudins) and cytoplasmic (ZO-1) TJ proteins [26]. It was reported that changes in the expression of gill TJ proteins could contribute to the major permeability variation in Southern Flounder [27].…”

Tight junction protein gene expression patterns and changes in transcript abundance during development of model fish gill epithelia

“…Recent studies have shown select TJ proteins of the gill epithelium to be sensitive to environmental change as well as endocrine factors that mediate the systemic response of fishes to varying environmental conditions (for a review see Chasiotis et al, 2012a). These TJ proteins include a number of claudin as well as transmembrane TJ proteins such as occludin (Ocln) and Tric (Chasiotis et al, 2012b;. In addition, cortical proteins such as zonula occludens 1 (ZO-1) have been reported to alter in response to environmental or systemic change (Chasiotis et al, 2012b).…”

“…These TJ proteins include a number of claudin as well as transmembrane TJ proteins such as occludin (Ocln) and Tric (Chasiotis et al, 2012b;. In addition, cortical proteins such as zonula occludens 1 (ZO-1) have been reported to alter in response to environmental or systemic change (Chasiotis et al, 2012b). However, despite an increasing number of studies examining gill epithelium TJ proteins in relation to changes in the external environment, the contribution of gill epithelium TJ proteins to the establishment and maintenance of paracellular permeability properties in this tissue remains poorly understood.…”