Actions of 1,25(OH)2-vitamin D3 on the cellular cycle depend on VDR and p38 MAPK in skeletal muscle cells

Abstract

Previously, we have reported that 1,25(OH) 2 -vitamin D 3 (1,25D) activates p38 MAPK (p38) in a vitamin D receptor (VDR)-dependent manner in proliferative C2C12 myoblast cells. It was also demonstrated that 1,25D promotes muscle cell proliferation and differentiation. However, we did not study these hormone actions in depth. In this study we have investigated whether the VDR and p38 participate in the signaling mechanism triggered by 1,25D. In C2C12 cells, the VDR was knocked down by a shRNA, and p38 was specifically inhibited using SB-203580. Results from cell cycle studies indicated that hormone stimulation prompts a peak of S-phase followed by an arrest in the G0/G1-phase, events which were dependent on VDR and p38. Moreover, 1,25D increases the expression of cyclin D3 and the cyclin-dependent kinase inhibitors, p21Waf1/Cip1 and p27 Kip1 , while cyclin D1 protein levels did not change during G0/G1 arrest. In all these events, p38 and VDR were required. At the same time, a 1,25D-dependent acute increase in myogenin expression was observed, indicating that the G0/G1 arrest of cells is a pro-differentiative event. Immunocytochemical assays revealed co-localization of VDR and cyclin D3, promoted by 1,25D in a p38-dependent manner. When cyclin D3 expression was silenced, VDR and myogenin levels were downregulated, indicating that cyclin D3 was required for 1,25D-induced VDR expression and the concomitant entrance into the differentiation process. In conclusion, the VDR and p38 are involved in control of the cellular cycle by 1,25D in skeletal muscle cells, providing key information on the mechanisms underlying hormone regulation of myogenesis.

Vitamin D and VDR in cancer cachexia and muscle regeneration

“…To investigate this point, the effects of VitD treatment were studied in vitro on C2C12 myocyte cultures. VitD addition to the culture medium slowed C2C12 myoblast proliferation in a dose- and VDR-dependent manner (data not shown), confirming previous observations [24, 27]. Moreover, attempts to produce VDR overexpressing C2C12 myoblasts by gene transfection were revealed to be unsuccessful, suggesting that high VDR levels might be toxic, in myoblasts at least, lowering proliferation rates and eventually leading to cell death (data not shown).…”

Low 25-OH vitamin D levels at time of diagnosis and recurrence of ovarian cancer

“…The present study confirmed the findings from other cancers and demonstrated that 25-OH vitamin D is decreased at time of diagnosis in nearly all patients affected by ovarian cancer and that only a small percentage of patients affected by gynecological benign diseases had levels below the cutoff for 25-OH vitamin D [10,28]. These results could be interpreted according to the 25-OH vitamin D antiproliferative effects and its ability to block cell mitosis in the G1 phase [29].…”

Association of hypovitaminosis D with triceps brachii muscle fatigability among older women: Findings from the EPIDOS cohort

“…Results of several lines of experimentation support an action of vitamin D on muscles. In particular, the presence of vitamin D receptors (VDRs) has been revealed in muscle cells [5], both in the nucleus and the cytoplasmic membrane [25]. The genomic action of vitamin D appears involved in various phenomena including calcium influx into muscle cells, membrane phosphate transport, phospholipids metabolism, and muscle fiber proliferation and differentiation [26,27].…”