Aloin attenuates high-glucose-induced oxidative and inflammatory damage in renal cells via AMPK/Nrf2 signaling

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease, with proximal tubular injury and oxidative stress playing pivotal roles in its progression. The AMPK-Nrf2 signaling axis is a key regulator of antioxidant defense, but its modulation by Aloin in DN-relevant renal models remains insufficiently characterized. Aloin, a natural anthraquinone glycoside from Aloe species, exhibits antioxidant, anti-inflammatory, and anti-fibrotic properties in non-renal systems. This study investigated whether Aloin protects renal cells from high-glucose-induced injury and whether AMPK and Nrf2 contribute to these protective responses.

Human renal proximal tubular epithelial cells (HK-2) and human renal glomerular endothelial cells (HRGECs) were exposed to high glucose (HG, 30 mM) for 48 h with or without Aloin (25 or 50 µM). Functional assays included CCK-8 cell viability, colony formation, and wound healing migration analysis. mRNA expression of oxidative stress-related, inflammatory, fibrotic, and phenotype-associated markers, including VIM and CDH1, was quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). siRNA-mediated knockdown of PRKAA1 (AMPK) or NFE2L2 (Nrf2) was performed to assess mechanistic involvement, with gene silencing confirmed by RT-qPCR and Western blotting. For exploratory in vivo validation, male db/db mice received oral Aloin at 25 mg/kg/day for 8 weeks, while age-matched db/m and db/db mice received vehicle (n = 6 per group).

HG exposure reduced proliferation and clonogenic capacity while increasing wound closure under serum-free conditions in both HK-2 cells and HRGECs, accompanied by upregulation of TNF, CCL2, TGFB1, COL1A1, and VIM, and downregulation of NFE2L2, SOD1, PRKAA1, and CDH1. Aloin treatment dose-dependently restored proliferation, reduced migration, and normalized gene expression patterns, with 50 µM producing near-complete reversal toward normal glucose controls. PRKAA1 knockdown in HK-2 cells and NFE2L2 knockdown in HRGECs substantially attenuated Aloin-associated protective responses, supporting the functional involvement of AMPK and Nrf2 in these cell-specific effects.

Aloin attenuated high-glucose-induced injury in cultured renal tubular epithelial and glomerular endothelial cells, with loss-of-function experiments supporting the involvement of AMPK and Nrf2 in these responses. Exploratory validation in db/db mice further showed reductions in albuminuria, serum creatinine, and mesangial matrix expansion, accompanied by restoration of renal AMPK-Nrf2 signaling. However, the 25 and 50 µM concentrations used in vitro cannot be directly equated with the 25 mg/kg/day oral dose used in mice, and plasma exposure, renal tissue concentrations, pharmacokinetics, and systemic safety were not determined. Additional pharmacokinetic, dose-ranging, and toxicological studies are required before the therapeutic relevance of Aloin can be established.