Exploring the impact of naltrexone on the THBS1/eNOS/NO pathway in osteoporotic bile duct-ligated rats

Abstract

Hepatic osteodystrophy, a prevalent manifestation of metabolic bone disease, can arise in the context of chronic liver disease. The THBS1-eNOS-NO signaling pathway plays a pivotal role in the maturation of osteoclast precursors. This study aimed to investigate the impact of Naltrexone (NTX) on bone loss by examining the THBS1-eNOS-NO signaling pathways in bile duct ligated (BDL) rats. Male Wistar rats were randomly divided into five groups (n = 10 per group): control, sham-operated + normal saline, BDL + normal saline, sham-operated + NTX (10 mg/kg), and BDL + NTX. Parameters related to liver injury were measured at the study's conclusion, and Masson-trichrome staining was employed to evaluate collagen deposition in liver tissue. Bone THBS-1 and endothelial nitric oxide synthase (eNOS) expression levels were measured using real-time PCR, while the level of bone nitric oxide (NO) was assessed through a colorimetric assay. NTX treatment significantly attenuated the BDL-induced increase in circulating levels of liver enzymes and bilirubin. THBS-1 expression levels, elevated after BDL, were significantly suppressed following NTX administration in the BDL + NTX group. Despite no alterations in eNOS expression between groups, the bone NO level, significantly decreased in the BDL group, was significantly reduced by NTX in the BDL + NTX group. This study partly provides insights into the possible molecular mechanisms in BDL-induced osteoporosis and highlights the modulating effect of NTX on these pathways. Further research is needed to establish the impact of NTX on histomorphometric indexes.

Figure 1

Representative hematoxylin–eosin-stained sections of rat tibia demonstrating cortical thickness/area and trabecular thickness/number in all study groups including controls, sham-operated and bile duct ligation (BDL) animals injected with saline, and sham-operated and BDL rats receiving naltrexone (NTX) (scale bar for all images: 0.1mm). Bar graphs show the comparison of treatment groups with controls (baseline) with *, ***, and NS representing < 0.05, < 0.0001, and no significant differences, respectively.

Figure 2

Optical density of the skull and mandible reference points in addition to the mRNA expression levels of thrombospondin-1 (THBS-1), endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) among the study groups. Bar graphs show the comparison of treatment groups with controls (baseline) with *, **, and NS representing < 0.05, < 0.001, and no significant differences, respectively.