Tauroursodeoxycholic Acid Mitigates Oxidative Stress and Promotes Differentiation in High Salt-Stimulated Osteoblasts via NOX1 Mediated by PGC-1α

Background: High-salt diet (HSD) is a pivotal risk factor for osteoporosis (OP). Accumulating evidence has supported that tauroursodeoxycholic acid (TUDCA), a naturally produced hydrophilic bile acid, exerts positive effects on the treatment of OP. This study is committed to shedding light on the impacts of TUDCA on high salt-treated osteoblasts and probing into its underlying mechanisms of action. Methods: Cell counting kit-8 (CCK-8) assay was used to determine the viability of osteoblasts. Alkaline phosphatase (ALP) staining and Alizarin red S (ARS) staining were used to measure osteoblast differentiation. Reverse transcription-quantitative PCR (RT-qPCR) and western blot were used to examine the expression of osteogenic markers. Western blot was also used to analyze the expression of superoxide dismutase-2 (SOD2), peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1 alpha), and NADPH oxidase 1 (NOX1). The production of reactive oxygen species (ROS) was evaluated via dichloro-dihydrofluorescein diacetate (DCFH-DA) assay. Following PGC-1 alpha knockdown in TUDCA-pretreated osteoblasts exposed to NaCl, the aforementioned functional experiments were implemented again. Results: MC3T3-E1 cell viability was not significantly impacted by increasing concentrations of TUDCA. However, in NaClexposed MC3T3-E1 cells, the viability loss, oxidative stress, and decline of differentiation were all dose-dependently obstructed by TUDCA treatment. Moreover, NaCl exposure reduced PGC-1 alpha expression and increased NOX1 expression, which was then reversed by TUDCA. PGC-1 alpha deletion partially abolished the effects of TUDCA on PGC-1 alpha and NOX1, differentiation, and oxidative stress in NaCl-treated osteoblasts. Conclusions: TUDCA might protect against high salt-induced OP via modulation of NOX1 mediated by PGC-1 alpha.