Knockdown of lncRNA XR_877193.1 suppresses ferroptosis and promotes osteogenic differentiation via the PI3K/AKT signaling pathway in SONFH

Abstract

Ferroptosis is a novel form of regulated cell death characterized by the iron-dependent accumulation of lipid peroxides. Recent research has suggested that ferroptosis in osteoblasts contributes to steroid-induced osteonecrosis of the femoral head (SONFH). However, the relationship between ferroptosis and SONFH remains unclear. In this study, in vitro experiments show that dexamethasone (Dex) treatment reduces the expressions of key ferroptosis regulators, SLC7A11 and GPX4, in MC3T3-E1 cells. This reduction leads to a decrease in intracellular glutathione (GSH) levels, accompanied by elevated levels of total iron, malondialdehyde (MDA), and reactive oxygen species (ROS). Importantly, the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively reverses Dex-induced ferroptosis in MC3T3-E1 cells. Furthermore, RNA-seq analysis reveals that the long noncoding RNA (lncRNA) XR_877193.1 is significantly upregulated in Dex-treated MC3T3-E1 cells. Functional studies demonstrate that the knockdown of lncRNA XR_877193.1 promotes osteogenic differentiation by inhibiting Dex-induced ferroptosis in MC3T3-E1 cells, whereas its overexpression exacerbates cell death via ferroptosis. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis reveals that the differentially expressed lncRNA XR_877193.1 is enriched in ferroptosis-related pathways, including the PI3K/AKT signaling pathway. Moreover, PI3K/AKT inhibitors reverse ferroptosis in MC3T3-E1 cells inhibited by lncRNA XR_877193.1 knockdown. Collectively, our findings indicate that lncRNA XR_877193.1 knockdown exerts anti-ferroptosis effects by stimulating the PI3K/AKT signaling pathway, suggesting a promising therapeutic strategy for attenuating SONFH.

1. Introduction

Glucocorticoids (GCs) are widely used for the treatment of inflammatory and autoimmune diseases or cancers, including arthritis, systemic lupus erythematous and relapsed or refractory multiple myeloma [1,2]. However, in recent years, numerous studies have demonstrated that excessive GC usage inhibits osteoblast proliferation and promotes their death, thus resulting in the occurrence of steroid-induced osteonecrosis of the femoral head (SONFH) in patients [3]. With the widespread misuse of glucocorticoids, the incidence of this disease has been steadily increasing [4]. Clinically, this condition primarily manifests as hip pain, restricted hip joint mobility, and, in severe cases, may lead to bone collapse [5]. Therefore, early diagnosis and intervention are crucial for preventing the progression of this disease.

Osteoblasts are key cells in bone formation. GCs reduce the proliferation and differentiation of osteoblast precursor cells by downregulating key markers such as Runx2, Osterix, and ALP [6]. GCs also induce osteoblast death, diminishing their overall numbers and further reducing bone formation over time [7,8]. Additionally, GC exposure decreases ALP activity, impairing mineralization of the bone matrix and resulting in weaker, less dense bone [9]. Although the primary effect of GCs is on osteoblasts, they also indirectly increase osteoclast activity. This occurs through the upregulation of RANKL expression in osteoblasts and a reduction in osteoprotegerin, which normally inhibits RANKL. Increased osteoclast activity accelerates bone resorption, compounding the negative effects on bone formation and contributing to osteoporosis and SONFH [10]. Understanding these mechanisms may reveal potential therapeutic targets for SONFH.