<scp> <i>Panax notoginseng</i> </scp> Saponins Prevents Atherosclerosis and Reverse Steroid‐Resistance in Lupus Nephritis via Promoting the “ <scp>M2</scp> ‐Polarization of Macrophages— <scp>PPARγ</scp> ” Positive Regulation

Lupus nephritis (LN) is a severe autoimmune disease often complicated by steroid resistance (SR), leading to treatment failure and poor prognosis like atherosclerosis (AS). Our study found that Panax notoginseng saponins (PNS) improve lipid metabolism and prevent AS in steroid-resistant LN by up-regulating PPARγ, though mechanisms are unclear. Recent research highlights the roles of macrophages, with M1 Mø promoting inflammation and M2 Mø providing protection, as PPARγ influences Mø's polarization, linking it to inflammation and M2 polarization, necessitating further investigation. Therefore, we conduct this study to investigate the regulatory effect of PNS on the "Mø M2 polarization-PPARγ" positive regulation, endeavoring to elucidate its therapeutic potential of delaying AS and reversing SR in LN. PPARγ expression in polarized Mø was measured via PCR and WB, while M1/M2 biomarkers and cytokines, influenced by PPARγ modulation, were assessed using flow cytometry and ELISA. In mouse Mø treated with PNS, IL-4, or both, PPARγ and cytokines were measured. ICR and MRL/lpr mice were used to establish an in vivo SR model to confirm PNS's role in M2 polarization of Mø and AS protection by analyzing blood lipid levels, iNOS, Lp(a), and apoptosis rates through WB, immunohistochemistry, HE-staining, and TUNEL. PNS's efficacy in renal protection and SR reversal was evaluated through Scr, BUN, urine protein, renal pathology, and P-gp; MDR1 expression was assessed via biochemical detection, HE-staining, flow cytometry, and WB. This study confirmed that PNS upregulates PPARγ and promotes M2 polarization, improving abdominal aorta pathology and delaying AS. It also enhances renal function and reverses SR by reducing P-gp and MDR1. This study shows that PNS promotes Mø polarization to M2 and enhances PPARγ expression, effectively preventing AS, improving renal function, and reversing SR in LN, offering insights for LN treatment and expanding PNS's therapeutic benefits for future research.