Epimedium flavonoids improve renal tissue fibrosis in naturally aging rats through the TGF – β 1/Smad3 signaling pathway
With the advent of population aging, the incidence rate of age-related diseases shows a significant growth trend. According to big data statistics, the prevalence of chronic kidney disease has reached 10% in the past 10 years. The kidneys are one of the most important metabolic organs in the human body, playing a crucial role in maintaining normal life activities. As age increases, glomerular sclerosis, tubular atrophy, and interstitial fibrosis associated with aging cause changes in renal structure and hemodynamics, leading to progressive deterioration or even loss of renal function. Renal fibrosis is the end-stage manifestation of chronic kidney disease. Once it occurs, it seriously affects the quality of life and survival time of patients. Therefore, finding effective drugs to prevent and treat age-related fibrosis has important medical value and social significance. Actively improving chronic damage and fibrosis of kidney tissue is an important link in preventing and treating chronic kidney disease.

Herba Epimedii, also known as Xianling Pi, is a common traditional natural kidney tonifying Chinese medicine. It has a warm nature, travels through the liver and kidney meridians, and has the effects of tonifying the kidneys, strengthening muscles and bones, dispelling wind and dampness. Its medicinal history is long. Total flavonoids of Herba Epimedii (TFE) are the active ingredients of Epimedium. Modern pharmacological studies have shown that TFE has the effect of improving osteoporosis, cardiovascular disease, and testicular lesions. At the same time, it can resist aging through various pathways such as promoting cell proliferation, antioxidant, and anti-inflammatory effects, and has great research value. Previous studies have shown that TFE can improve the secretion function of testicular Sertoli cells in naturally aging rats by regulating the IRE1 α/XBP1 signaling pathway; TFE can also improve brain inflammation and delay brain aging in naturally aging rats by inhibiting the MAPK/NF κ B signaling pathway. Multiple reports have shown that Epimedium can effectively resist aging in multiple organs, but there are few reports on whether it can improve fibrosis caused by kidney aging. Therefore, this study aims to explore the effects and mechanisms of TFE on renal tissue fibrosis in naturally aging rats by observing its effects on renal morphology, function, as well as the expression levels of α SMA, TGF – β 1, and Smad3 proteins. This will provide strong experimental evidence for enriching the prevention and treatment of aging related diseases with Epimedium.

At present, the percentage of elderly people in China’s total population has reached 17%. Aging is one of the main factors contributing to chronic kidney disease, and the incidence of complications in elderly patients has also doubled. The occurrence and development of kidney disease will seriously threaten the survival time and quality of the elderly population. Therefore, exploring effective intervention measures can have a certain improvement effect on the outcome of chronic kidney disease patients, and for the aging process, preventing kidney aging may be one of the ways to prevent and treat age-related kidney disease.

Renal interstitial fibrosis (RIF) is a pathological manifestation of various chronic kidney diseases that progress to the end-stage, and is also one of the main manifestations of aging kidneys and a major cause of renal failure. Phenotypic transdifferentiation of renal tubular epithelial cells is the core link in the occurrence of renal interstitial fibrosis, and α SMA, as a highly specific transdifferentiation marker, is one of the markers for fibrosis. Through HE staining and Masson staining, it can be observed that the collagen fibers in the kidney tissue of naturally aging rats are significantly increased, and immunohistochemistry shows a significant increase in the expression of α SMA. After gavage treatment with different concentrations of Epimedium total flavonoids, the collagen fiber content in the kidney tissue decreases, and the expression of α SMA decreases. The high-dose group has a significant effect, indicating that TFE can improve renal interstitial fibrosis by reducing the production of collagen fibers.

As age increases, antioxidant capacity gradually decreases, and the body’s ability to produce and eliminate free radicals becomes imbalanced. Oxygen free radicals continue to accumulate, leading to cell damage and functional decline. SOD is an antioxidant enzyme that uses free radicals as substrates and combines with O2 to generate H2O2, which is the main substance for clearing oxygen free radicals in the body. Oxygen free radicals induce peroxidation of polyunsaturated fatty acids to form lipid peroxides such as MDA, causing cellular damage. The content of MDA can reflect the degree of lipid peroxidation in the body, and together with SOD, it reflects the antioxidant capacity. The experimental results of this study showed that compared with young rats, the SOD activity in the kidney tissue of naturally aging rats decreased significantly, while the MDA content increased. However, the SOD activity of rats given Epimedium total flavonoids by gavage increased compared to the model group, while the MDA content decreased. This indicates that the antioxidant capacity of aging rats decreases, while the antioxidant capacity increases after oral administration of TFE.

With the occurrence of aging, the compensatory ability of the body’s metabolism gradually weakens, and cells are activated by the stimulation of metabolic products, producing a series of inflammatory factors, thereby inducing the production and infiltration of inflammatory cells. We also observed extensive inflammatory cell infiltration in the kidney tissue of aging rats through HE staining, and the inflammatory infiltration was significantly reduced in the group treated with total flavonoids of Epimedium, indicating that total flavonoids of Epimedium can protect the kidneys by reducing inflammatory cell infiltration. This is similar to the anti-inflammatory effect of total flavonoids in Epimedium reported in previous studies by Xia Shijin and others.

TGF – β is a cytokine that strongly induces glomerulosclerosis and renal fibrosis. It mainly promotes the recruitment and activation of inflammatory cells, mediates the differentiation of renal tubular epithelial cells into mesenchymal cells, and promotes the synthesis and deposition of extracellular mechanisms. Smad protein is an intracellular kinase substrate of TGF – β 1 receptor. As an important mediator of TGF – β signaling, it can directly activate genes encoding transcription regulatory factors and signal transduction through the DNA binding domain of early target genes of TGF – β. Therefore, the TGF – β/Smad signaling pathway plays an important role in the process of chronic renal fibrosis injury. This indicates that finding effective drugs targeting TGF – β 1 has a great potential to improve fibrosis progression. In this study, the mRNA and protein levels of TGF – β 1 and Smad3 in renal tissue of naturally aging rats were significantly increased, while they were decreased after oral administration of TFE, and the high-dose effect was significant. This suggests that total flavonoids of Epimedium may improve renal tissue fibrosis by inhibiting the expression of TGF – β 1 and reducing the expression of Smad3.

In summary, TFE has the effect of improving renal fibrosis in naturally aging SD rats, which may be related to reducing the protein expression levels of TGF – β 1, Smad3, and α SMA in the kidney tissue of naturally aging rats, as well as improving aging renal fibrosis by reducing inflammatory cell infiltration and alleviating oxidative stress damage to the kidneys. At present, studies have confirmed that total flavonoids of Epimedium have anti-inflammatory, antioxidant, anti-aging and other effects in multiple organs. However, there is no research report on its ability to improve fibrosis caused by aging in kidney tissue, which is an important participant in body metabolism. Therefore, this study has certain innovation and application value, providing experimental basis and application basis for the clinical prevention and treatment of Epimedium in a series of diseases related to aging kidney fibrosis.