Lupus nephritis serum induces changes in gene expression in human glomerular endothelial cells, which is modulated by L-sepiapterin: Implications for redox-mediated endothelial dysfunction
Lupus nephritis (LN) is characterized by renal endothelial dysfunction, which contributes to progressive kidney injury. Endothelial nitric oxide synthase (eNOS) plays a modulating role in LN, as genetic ablation of the eNOS enzyme worsens disease. Serum from patients with active LN induces uncoupling of eNOS homodimers, leading to superoxide (SO) rather than nitric oxide (NO) production by eNOS. This uncoupling is reversed with L-sepiapterin (L-Sep). This study was designed to further examine changes in gene expression in glomerular endothelial cells induced by LN serum and whether treatment with L-Sep can ameliorate these changes. Methods Primary human renal glomerular endothelial cells (HRGECs) were cultured with serum from non-lupus controls (HC), LN patients during remission (LN rem), or LN patients during flare (LN flare) with and without L-Sep. Bulk RNA sequencing was performed on RNA isolated from cultured cells. Differential gene expression was determined, and pathway and gene enrichment analyses were performed on differentially expressed genes. Results L-Sep treatment induced differential gene expression after culture in HRGECs cultured with LN flare serum. Addition of L-Sep induced genes involved in promoting endothelial function and  enriched for pathways of NO biosynthetic and metabolic processes, fatty acid and lipid biosynthesis, neurotransmitter biosynthesis, reactive oxygen biosynthesis, vascular endothelial growth factor production, and regulation of smooth muscle contraction. Conclusions These results indicate that glomerular endothelial cells can mount an active inflammatory response in an LN serum environment. More importantly, L-Sep modulates gene expression in a fashion consistent with reduction of oxidative stress and increased NO production. These findings provide the rationale to target endothelial dysfunction to modulate LN with L-Sep as a therapeutic. Overall design: RNAseq profiling of human renal glomerular endothelial cells cultured with serum from non-lupus controls (HC) and from LN patients during flare (LN flare) with and without L-Sep