C Zhou1, H Q Chen, R Reeves, N Agarwal, P R Cammarata. 1. Department of Anatomy and Cell Biology, University of North Texas Health Science Center at Fort Worth/North Texas Eye Research Institute 76107.
Abstract
PURPOSE: To examine the effect of hypertonicity on the induction of the Na(+)-myo-inositol (Na(+)-MI) cotransporter(s) in cultured bovine lens epithelial cells (BLECs). METHODS: Na(+)-MI cotransporter 626-bp reverse transcription-polymerase chain reaction product amplified from lens cell RNA and aldose reductase (AR) cDNA probes were used to measure respective mRNA content by Northern blot analysis. RESULTS: Northern blot analysis of BLEC mRNA hybridized to Na(+)-MI cotransporter cDNA showed that Na(+)-MI cotransporter mRNA increased when secondary cultures of BLECs were exposed to physiological medium supplemented with 116 mmol/l NaCl. A time course further revealed a maximal increase in Na(+)-MI cotransporter mRNA by 8 hours. Thereafter, the level of Na(+)-MI cotransporter mRNA steadily declined for the duration of the 72-hour incubation period despite continuous exposure of BLECs to hypertonicity. AR mRNA levels maximally increased by 24 h of cell exposure to hypertonic condition. Unlike Na(+)-MI cotransporter mRNA, AR mRNA remained elevated throughout the duration of the experiment. Hypertonic exposure resulted in a steady state accumulation of myo-inositol and sorbitol for 6 days. Inhibition of sorbitol formation prompted the intracellular myo-inositol content to a higher level. CONCLUSIONS: These data suggest that enhanced MI transport and accumulation, as an adaptive osmoregulatory response to hypertonicity in cultured BLECs, is a primary, early-onset, protective mechanism against water stress, succeeded by, enhanced sorbitol formation and accumulation, a secondary, late-onset protective mechanism. The lens appears to respond to the preliminary stages of hyperosmotic stress by induction of Na(+)-MI cotransporter mRNA, indicating that the myo-inositol carrier protein(s) play an initial responsive role in the management of osmotic stress. Lens water stress management is interactive because myo-inositol and sorbitol levels are regulated in concert.
PURPOSE: To examine the effect of hypertonicity on the induction of the Na(+)-myo-inositol (Na(+)-MI) cotransporter(s) in cultured bovine lens epithelial cells (BLECs). METHODS: Na(+)-MI cotransporter 626-bp reverse transcription-polymerase chain reaction product amplified from lens cell RNA and aldose reductase (AR) cDNA probes were used to measure respective mRNA content by Northern blot analysis. RESULTS: Northern blot analysis of BLEC mRNA hybridized to Na(+)-MI cotransporter cDNA showed that Na(+)-MI cotransporter mRNA increased when secondary cultures of BLECs were exposed to physiological medium supplemented with 116 mmol/l NaCl. A time course further revealed a maximal increase in Na(+)-MI cotransporter mRNA by 8 hours. Thereafter, the level of Na(+)-MI cotransporter mRNA steadily declined for the duration of the 72-hour incubation period despite continuous exposure of BLECs to hypertonicity. AR mRNA levels maximally increased by 24 h of cell exposure to hypertonic condition. Unlike Na(+)-MI cotransporter mRNA, AR mRNA remained elevated throughout the duration of the experiment. Hypertonic exposure resulted in a steady state accumulation of myo-inositol and sorbitol for 6 days. Inhibition of sorbitol formation prompted the intracellular myo-inositol content to a higher level. CONCLUSIONS: These data suggest that enhanced MI transport and accumulation, as an adaptive osmoregulatory response to hypertonicity in cultured BLECs, is a primary, early-onset, protective mechanism against water stress, succeeded by, enhanced sorbitol formation and accumulation, a secondary, late-onset protective mechanism. The lens appears to respond to the preliminary stages of hyperosmotic stress by induction of Na(+)-MI cotransporter mRNA, indicating that the myo-inositol carrier protein(s) play an initial responsive role in the management of osmotic stress. Lens water stress management is interactive because myo-inositol and sorbitol levels are regulated in concert.
Authors: Eugene Serebryany; Sourav Chowdhury; Christopher N Woods; David C Thorn; Nicki E Watson; Arthur A McClelland; Rachel E Klevit; Eugene I Shakhnovich Journal: Elife Date: 2022-06-20 Impact factor: 8.713