Effect of spermidine on endothelial function in Systemic Lupus Erythematosus (SLE)

Impaired endothelial function has been shown in SLE patients and lupus-prone mice. Emerging evidence supports impaired mitochondrial dynamics and mitophagy contribute to SLE and endothelial dysfunction. Spermidine is a natural polyamine that stimulates mitophagy by activating the PINK1-Parkin pathway and can improve endothelial function. However, the effect of spermidine on mitophagy and vascular function in SLE has not been explored. To address this gap, 9-week-old female lupus-prone (MRL/lpr) and healthy control (MRL/MpJ) mice were randomly assigned into one of two groups, spermidine treatment (Lpr T and MpJ T) or control (Lpr C and MpJ C). Treated mice received spermidine (3mM) via drinking water for 8 weeks. After 8 weeks of treatment, endothelium-dependent vasorelaxation to acetylcholine (ACh) and endothelium-independent vasorelaxation to sodium nitroprusside (SNP) were measured in thoracic aortas using a wire myograph. Maximal responses to ACh were significantly impaired in Lpr C (67.1 ± 8.7, n = 11) compared to Mp C (90.3 ± 3.1, n = 13) (p = 0.01). Spermidine improved endothelial function in thoracic aorta from Lpr T (90.3 ± 2.8, n = 13) compared to Lpr C (p = 0.03). Maximal responses to SNP were not significantly different across the groups. Thoracic and abdominal aortas were used for measurements of protein content (n = 3-4/group) and gene expression (n = 4/group), respectively. There were strain differences in the mRNA expression of endothelial nitric oxide synthase ( Nos3) between Lpr C (0.65 ± 0.14) and MpJ C (1.00 ± 0.16) (p = 0008). In MpJ mice, Nos3 mRNA expression was significantly higher in the aorta from the MpJ T (1.47 ± 0.39) compared to MpJ C (p = 0.04). No significant differences were found in the Nos3 expression between Lpr groups. Vascular cell adhesion molecule 1 (Vcam1) is an indicator of inflammation and is associated with atherosclerosis susceptibility. Protein content of Vcam1 was significantly lower in Lpr T (3.73 ± 0.61) compared to Lpr C (8.49 ± 2.58) (p = 0.04) and gene expression of Vcam1 was also lower in Lpr T compared to Lpr C, suggesting spermidine decreases the inflammatory responses in vessels from SLE mice. Protein content of Parkin was measured as a marker of mitophagy. Parkin was significantly lower in Lpr C (0.38 ± 0.61) compared to MpJ C (1.00 ± 0.09) (p = 0.004), suggesting lower mitophagy in aorta from SLE mice. Parkin content in Lpr T was similar to MpJ C. Collectively, these results demonstrate the beneficial effects of spermidine treatment on endothelial function in SLE mice and suggest inflammation and altered mitophagy contribute to endothelial dysfunction in SLE. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.