Baicalin Reduces Renal Inflammation in Mesangial Proliferative Glomerulonephritis through Activation of Nrf2/ARE and PI3K/AKT Pathways

Abstract

Objective: Mesangial proliferative glomerulonephritis (MPGN) is a prevalent form of primary glomerulonephritis, distinguished by the proliferation of mesangial cells and the accompanying inflammatory response. Baicalin, the active ingredient in the Scutellaria baicalensis Georgi plant, has been observed to have a protective effect on the kidneys. However, its specific impact on MPGN has yet to be studied widely. Hence, this study aimed to investigate the effect on MPGN and the underlying mechanisms of Baicalin.

Methods: Thirty-six Sprague-Dawley (SD) rats, aged 6 to 8 weeks, were randomly allocated into different subgroups: control, model, benazepril, and three baicalin subgroups (low, medium, and high dose), each consisting of six rats. The concentrations of 24-hour urinary protein, blood urea nitrogen (BUN), serum creatinine (SCr), triglycerides (TG), total cholesterol (TC), interleukins (IL-1α, IL-2, IL-10), and interferon-γ (IFN-γ) were measured with biochemistry. The pathological alterations in the renal tissue were examined using Hematoxylin and Eosin (HE) along with Periodic Acid-Schiff (PAS) staining. Concurrently, the extent of apoptosis was evaluated using TdT-mediated dUTP nick end labeling (TUNEL) staining. In vitro, mesangial cells were exposed to 30 μg/mL lipopolysaccharide for 24 h, with or without varying concentrations of baicalin (10, 20, 40 μM). MTT assay was applied to estimate cell activity, flow cytometry to evaluate the cell cycle, and 5-ethynyl-2-deoxyuridine (EdU) detection to measure cell proliferation. IL-1α, IL-2, IL-10, and IFN-γ concentrations in the cell supernatant were assayed with biochemistry. Furthermore, the expression of apoptosis-related proteins, concluding BCL2-Associated X (Bax), Bcl-2, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), and caspase-1, NF-E2-related factor 2/antioxidant response element (Nrf2/ARE) pathway-related proteins (Nrf2 and HO-1), and phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) pathway-related proteins (p-PI3K, PI3K, p-AKT, and AKT) in both the renal tissue and cell supernatant were measured.

Results: Baicalin treatment significantly reduced the 24-hour urinary protein, serum levels of BUN, SCr, TG, TC, IL-1α, IL-2, IL-10, and IFN-γ in vivo experiments. Baicalin treatment also improved the pathological condition of renal tissue and decreased the occurrence of apoptosis. In vitro, findings confirmed that baicalin inhabits the proliferation of mesangial cells triggered by Lipopolysaccharide (LPS), induces a G1 phase cell cycle arrest, and reduces the concentrations of IL-1α, IL-2, IL-10, and IFN-γ. Baicalin also decreased the ratios of p-PI3K/PI3K and p-AKT/AKT while enhancing the levels of Nrf2 and HO-1 in both renal tissue and cell supernatant.

Conclusions: Baicalin can mitigate MPGN by impeding the proliferation and inflammation of mesangial cells by activating Nrf2/ARE and PI3K/AKT pathways.

Keywords: Inflammatory response; Nrf2/ARE pathway; PI3K/AKT pathway; baicalin; mesangial proliferative glomerulonephritis.