To observe the estrogen-like effects of fulvestrant and its influence on estrogen receptor expression of fulvestrant, this study set control, fulvestrant(500 μg/kg, ip), 17β-estradiol(100 μg/kg, ig)and 17β-estradiol + fulvestrant(100 μg/kg+500 μg/kg)groups. 7 days after dosing, mice were anesthetized; their uterine and vagina were collected. HE method was used to determine morphological changes of the tissues; protein expression levels of estrogen receptor alpha(ERα)and estrogen receptor beta(ERβ)in uterus and vagina were detected by immunohistochemistry and Western blot. The results showed that fulvestrant could obviously influence the growth of the uterus and vagina and expression of estrogen receptor in immature mice. Meanwhile, fulvestrant could significantly inhibit the growth of the uterus and vagina and increase estrogen receptors expression in immature mice. The research showed that fulvestrant has anti-estrogen-like effects, which may be related to the down-regulation of estrogen receptor expression in the target organs.

ObjectiveThis study aims to explore the mechanism of action of Huangqi Guizhi Wuwutang in treating rheumatoid arthritis （RA）-associated sarcopenia by regulating autophagy and improving skeletal muscle homeostasis based on network pharmacology，bioinformatics，machine learning，and animal experiments. MethodsActive ingredients and targets of Huangqi Guizhi Wuwutang were screened using the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform （TCMSP），PubChem，and SwissTargetPrediction databases. RA-related datasets were retrieved from the GEO database，and differential genes were screened. Sarcopenia-related targets were searched through GeneCards and the Comparative Toxicology Database （CTD），and autophagy-related gene sets were downloaded from the Human Autophagy Database （HADb）. Their intersection was analyzed to identify autophagy-related therapeutic targets，followed by enrichment analysis. A protein-protein interaction （PPI） network was constructed using the STRING database，and key targets were selected using multiple methods. Machine learning was applied to predict models based on the expression profiles of intersecting targets，and nomogram models were constructed based on key targets. Molecular docking of the top four active ingredients with key targets was performed using AutoDockVina. A collagen-induced arthritis （CIA） rat model was established using bovine type Ⅱ collagen，with SD rats divided into groups including a blank group，a model group，and low-，medium-，and high-dose groups of Huangqi Guizhi Wuwutang （2.44，4.88，and 9.76 g·kg^-1） and administered for five consecutive weeks. Joint scores and gastrocnemius muscle mass were recorded and analyzed after modeling. Hematoxylin and eosin （HE） staining and Masson's staining were used to observe pathological changes in muscle tissue. Immunofluorescence staining was applied to observe the protein expression levels of myosin heavy chain （MYHC） and insulin-like growth factor-1 （IGF-1） in skeletal muscle. Western blot was used to detect the protein expression levels of autophagy-related proteins ATG5，Beclin1，LC3B，muscle-specific proteins （MuRF1），MaFbx，and MYHC. Real-time quantitative reverse transcription PCR （Real-time PCR） was performed to measure the mRNA expression levels of ATG5，Beclin1，LC3B，MuRF1，MaFbx，and MYHC in muscle tissue. ResultsNetwork pharmacology revealed that Huangqi Guizhi Wuwutang shared 25 common targets with autophagy genes related to RA-associated sarcopenia. The PPI network and machine learning identified six key targets，which were primarily involved in autophagy and inflammatory pathways. Animal experiments showed that compared to the blank group，the model group had significantly higher joint scores （P<0.01） and lower gastrocnemius muscle index （P<0.01）. HE staining indicated a significant reduction in the cross-sectional area of gastrocnemius muscle fibers，with notable inflammatory cell infiltration and muscle atrophy in the model group. Masson's staining revealed obvious collagen fiber proliferation and deposition，with significant muscle fibrosis in the model group. The protein and mRNA expression levels of ATG5，Beclin1，LC3B，MuRF1，and MaFbx were significantly increased （P<0.01），while the protein expression of MYHC and IGF1 was significantly downregulated （P<0.01）. Compared with the model group，the high-dose group of Huangqi Guizhi Wuwutang showed significantly reduced protein and mRNA expression levels of ATG5，Beclin1，LC3B，MuRF1，and MaFbx （P<0.01） and increased protein expression levels of MYHC and IGF1 （P<0.01）. The cross-sectional area of muscle fibers increased，and the muscle cell morphology approached normal. Moreover，pathological abnormalities in the gastrocnemius muscle were significantly improved，with reduced collagen fiber proliferation （P<0.01）. ConclusionHuangqi Guizhi Wuwutang can mediate autophagy by regulating the expression of ATG5，Beclin1，LC3B，and IGF1，thereby reducing skeletal muscle catabolism and improving skeletal muscle homeostasis，which contributes to the treatment of RA-associated sarcopenia. The findings provide insight into the mechanisms underlying the effects of Huangqi Guizhi Wuwutang in the treatment of RA-related sarcopenia and offer a reference for its enhanced clinical application.