Intracellular Acid-Extruding Regulators and the Effect of Lipopolysaccharide in Cultured Human Renal Artery Smooth Muscle CellsReportar como inadecuado




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Homeostasis of the intracellular pH pHi in mammalian cells plays a pivotal role in maintaining cell function. Thus far, the housekeeping Na+-H+ exchanger NHE and the Na+-HCO3− co-transporter NBC have been confirmed in many mammalian cells as major acid extruders. However, the role of acid-extruding regulators in human renal artery smooth muscle cells HRASMCs remains unclear. It has been demonstrated that lipopolysaccharide LPS-induced vascular occlusion is associated with the apoptosis, activating calpain and increased Ca2+i that are related to NHE1 activity in endothelia cells. This study determines the acid-extruding mechanisms and the effect of LPS on the resting pHi and active acid extruders in cultured HRASMCs. The mechanism of pHi recovery from intracellular acidosis induced by NH4Cl-prepulse is determined using BCECF-fluorescence in cultured HRASMCs. It is seen that a the resting pHi is 7.19±0.03 and 7.10±0.02 for HEPES- and CO2-HCO3−- buffered solution, respectively; b apart from the housekeeping NHE1, another Na+-coupled HCO3− transporter i.e. NBC, functionally co-exists to achieve acid-equivalent extrusion; c three different isoforms of NBC: NBCn1 SLC4A7; electroneutral, NBCe1 SLC4A4; electrogenic and NBCe2 SLC4A5, are detected in protein-mRNA level; and d pHi and NHE protein expression-activity are significantly increased by LPS, in both a dose- and time- dependent manner, but NBCs protein expression is not. In conclusion, it is demonstrated, for the first time, that four pHi acid-extruding regulators: NHE1, NBCn1, NBCe1 and NBCe2, co-exist in cultured HRASMCs. LPS also increases cellular growth, pHi and NHE in a dose- and time-dependent manner.



Autor: Shih-Hurng Loh , Chung-Yi Lee, Yi-Ting Tsai, Shou-Jou Shih, Li-Wei Chen, Tzu-Hurng Cheng, Chung-Yi Chang, Chein-Sung Tsai

Fuente: http://plos.srce.hr/



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