1,25 dihydroxyvitamin D(3) activates sphingomyelin turnover in ROS17/2.8 osteosarcoma cells without...

Area of Science:

• Molecular Endocrinology
• Cell Biology
• Calcium Signaling

Background:

• 1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] is a crucial hormone regulating calcium homeostasis and bone metabolism.
• Sphingomyelin hydrolysis and ceramide generation are implicated in various cellular processes, including cell differentiation and apoptosis.
• The role of vitamin D in modulating sphingolipid metabolism and its downstream effects on calcium signaling remains incompletely understood.

Purpose of the Study:

• To investigate the effect of 1,25(OH)(2)D(3) on sphingomyelin turnover in ROS 17/2.8 osteosarcoma cells.
• To determine whether the generated ceramide mediates 1,25(OH)(2)D(3)-induced changes in intracellular calcium ([Ca(2+)](i)) or calcium uptake.
• To elucidate the relationship between vitamin D, sphingolipid metabolism, and calcium signaling in bone cells.

Main Methods:

• ROS 17/2.8 osteosarcoma cells were treated with 1,25(OH)(2)D(3).
• Cell-associated ceramide levels were measured over time.
• Intracellular free Ca(2+) ([Ca(2+)](i)) and Ca(2+) uptake were assessed following exposure to 1,25(OH)(2)D(3), exogenous ceramide, or sphingosine.

Main Results:

• 1,25(OH)(2)D(3) treatment led to a rapid increase in cell-associated ceramide levels, peaking at one hour.
• Neither 1,25(OH)(2)D(3) nor exogenous ceramide altered basal [Ca(2+)](i) levels.
• Exogenous sphingosine caused transient [Ca(2+)](i) elevations, but ceramide was not converted to sphingosine, and ceramide did not stimulate Ca(2+) uptake.

Conclusions:

• 1,25(OH)(2)D(3) effectively activates sphingomyelin turnover and ceramide generation in ROS 17/2.8 osteosarcoma cells.
• The generated ceramide is not responsible for the observed lack of change in [Ca(2+)](i) or Ca(2+) uptake.
• These findings suggest that 1,25(OH)(2)D(3)-induced calcium signaling pathways are independent of ceramide generated from sphingomyelin hydrolysis.