Higher Concentrations of Folic Acid Cause Oxidative Stress, Acute Cytotoxicity, and Long-Term Fibrogenic Changes in Kidney Epithelial Cells

Abstract

Kidney fibrosis is a common step during chronic kidney disease (CKD), and its incidence has been increasing worldwide. Aberrant recovery after repeated acute kidney injury leads to fibrosis. The mechanism of fibrogenic changes in the kidney is not fully understood. Folic acid-induced kidney fibrosis in mice is an established in vivo model to study kidney fibrosis, but the mechanism is poorly understood. Moreover, the effect of higher concentrations of folic acid on kidney epithelial cells in vitro has not yet been studied. Oxidative stress is a common property of nephrotoxicants. Therefore, this study evaluated the role of folic acidinduced oxidative stress in fibrogenic changes by using the in vitro renal proximal tubular epithelial cell culture model. To obtain comprehensive and robust data, three different cell lines derived from human and mouse kidney epithelium were treated with higher concentrations of folic acid for both acute and long-term durations, and the effects were determined at the cellular and molecular levels. The result of cell viability by the MTT assay and the measurement of reactive oxygen species (ROS) levels by the DCF assay revealed that folic acid caused cytotoxicity and increased levels of ROS in acute exposure. The cotreatment with antioxidant N-acetyl cysteine (NAC) protected the cytotoxic effect, suggesting the role of folic acid-induced oxidative stress in cytotoxicity. In contrast, the long-term exposure to folic acid caused increased growth, DNA damage, and changes in the expression of marker genes for EMT, fibrosis, oxidative stress, and oxidative DNA damage. Some of these changes, particularly the acute effects, were abrogated by cotreatment with antioxidant NAC. In summary, the novel findings of this study suggest that higher concentrations of folic acidinduced oxidative stress act as the driver of cytotoxicity as an acute effect and of fibrotic changes as a long-term effect in kidney epithelial cells.

Anemia of Chronic Kidney Disease—A Narrative Review of Its Pathophysiology, Diagnosis, and Management

“…Folic acid deficiency can result in anemia and other health issues, underscoring the importance of ensuring sufficient folic acid intake for overall health and to prevent complications [ 38 ]. It is essential to consider the potential impact of folic acid on oxidative stress, cytotoxicity, and fibrogenic changes in kidney epithelial cells, as higher concentrations of folic acid may have adverse effects on renal function [ 39 ]. Despite the relevance of folic acid in managing anemia, its role in CKD requires further investigation to optimize treatment strategies and improve patient outcomes.…”

Epithelial–mesenchymal plasticity in kidney fibrosis

“…The key kidney resident cells such as TECs are susceptible to damage and can respond to a variety of nephrotoxins in various ways (Li, Fu, & Liu, 2022). Several lines of evidence have reported that EMT of TECs plays a crucial role kidney fibrogenesis (Hu, Tang, Liu, Hu, & Pan, 2022; Kandel & Singh, 2022; Wang et al, 2022; Zhang, Xing, & Zhao, 2021). Initiation of fibrosis occurs when the toxins/stimuli cause TECs and kidney tissue to damage or dysfunction (Jorgacevic et al, 2022; Zhang et al, 2023).…”