Abstract
Background: The primary cilium, a microtubule-based cellular organelle, acts as a mechano-sensor for monitoring the fluid flow in cells. In kidneys, the primary cilia protrude into the tubular lumen from the tubular cells and therefore, directly contact pro-urine flow and components. However, it remains to be defined how the cilia are associated with kidney function and diseases. Here, we investigated whether water access restriction affects the cilia length in the renal tubular cells, whether cilia length changes are associated with kidney functions, and how cilia lengths are regulated. Methods: C57BL/6 mice were provided free access to water (control), but water supply was stopped for some mice for 24 to 48 h (water restriction). Among each group, some mice were administered with tubastatin A (10 mg/kg BW), a specific inhibitor of histone deacetylase 6 (HDAC6), daily from 2 days before water restriction. Cultured tubular epithelial cells were treated with either 10 or 20 mM NaCl or 20 mM mannitol with or without tubastatin A. Primary cilia were determined by immunofluorescence staining using acetylated-α-tubulin antibody or scanning electron microscope. Results: Water restriction shortened the primary cilia of kidney tubular epithelial cells along with increasing urine osmolality. Water restriction increased the activity of HDAC6 with increased the deacetylation of α-tubulin, a substrate of HDAC6 and a major comprising protein of microtubule of primary cilia. HDAC6 inhibitor blocked water restriction-induced primary cilia shortening along with the inhibition of α-tubulin deacetylation. In addition, HDAC6 inhibitor blocked the increase in water restriction-induced urine osmolality. Increases of NaCl or mannitol concentration in the medium for Madin-Darby canine kidney tubule cell culture shortened the cilia length and increased HDAC6 activity and α-tubulin deacetylation. HDAC6 inhibitor blocked those NaCl and mannitol-induced effects. Conclusions: Our data have demonstrated that water restriction shortened the primary cilia of kidney tubular cells via HDAC6 activation and α-tubulin deacetylation along with increasing urine osmolality, suggesting that the alteration of primary cilia length is an adaptive response to the water intake to maintain body water balance and that the primary cilia length regulation may be a therapeutic strategy of kidney diseases related to the body water and electrolyte imbalances.
Hydrogen sulfide, a gaseous signaling molecule, elongates primary cilia on kidney tubular epithelial cells by activating extracellular signal-regulated kinase
