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Targeting pathogenic endothelial dysfunction in lupus nephritis

Inflammation of the kidneys, called nephritis, is one of the most common and dangerous complications of lupus. Current nephritis therapies focus on targeting the immune cells that move into, and cause damage in, the kidneys. However, the cells that line the blood vessels, called endothelial cells, can also influence how tissues respond to inflammation. Endothelial dysfunction is a condition in which the endothelial cells fail to protect tissues. This dysfunction may cause cardiovascular disease and tissue inflammation, including inflammation in the kidneys and other organs. Dr. Oates has demonstrated that endothelial dysfunction worsens kidney disease in a mouse model of lupus and that improving endothelial function decreases inflammation in mice with lupus. Dr. Oates will use this grant to test if the existing medication sepiapterin, which has been shown to improve endothelial dysfunction in diabetes, can restore the protective role of endothelial cells and decrease kidney inflammation in mice with lupus nephritis. The research team will also study the effect of this drug on the cardiovascular system, as this is an important way to determine if the drug improves the function of endothelial cells.

 

What this study means for people with lupus

 

Findings from these studies will provide the foundation for future clinical studies with sepiapterin given to lupus patients to repair endothelial function. The sepiapterin therapy could possibly be used as an additional therapy in managing lupus nephritis and as a preventative therapy for lupus-induced cardiovascular diseases.

Endothelial cells (EC) are conditional innate effector cells activated by inflammatory stimuli to produce intracellular reactive oxygen species (ROS), a critical mechanism for inflammatory activation of EC. Functional endothelial nitric oxide synthase (eNOS) reduces inflammation in lupus nephritis (LN). Our laboratory has demonstrated that lack of eNOS accelerates aggressive LN pathology in murine LN and that LN serum induces adhesion and migration of neutrophils to human glomerular endothelial cells (HRGEC) with expression of platelet-derived growth factor BB (PDGFBB). Our preliminary studies indicate that eNOS dysfunction occurs in lupus through uncoupling of eNOS homodimers. This uncoupling reduces anti-inflammatory nitric oxide (NO) and increases pro-inflammatory reactive oxygen (ROS) production. We have also demonstrated that sepiapterin restores coupling and eNOS function in LN serum-treated HRGEC and reduces LN serum-induced PI3Kinase pathway and PDGFB gene expression. Restoring the anti-inflammatory action of eNOS is thus a promising therapeutic target in SLE. We hypothesize that targeting eNOS uncoupling will 1) reduce renal pathology, improve vascular function, and reduce biomarkers of inflammation and oxidative stress in murine LN and 2) lead to PDGFR/PI3Kinase/Akt signaling-dependent inflammatory gene expression in cultured ECs treated with LN serum. To address this overarching hypothesis, we propose the following specific aims: Aim 1) Determine the effect of recoupling eNOS on renal pathology, endothelial function, and pharmacodynamic markers of response in spontaneous murine LN treated with synthetic sepiapterin and/or mycophenolate. We will use the NZM2410 model of LN to study the effect of synthetic sepiapterin on renal pathology and single cell RNA expression with or without mycophenolate. Vascular endothelial function will be determined as a pharmacodynamic marker of response, while novel and conventional urine and serum biomarkers of inflammation and ROS production will be determined. Aim 2) Determine and target LN-serum-induced mechanisms of EC dysfunction in primary HRGEC treated with serum from patients with active LN. We will determine ROS/NO production in LN and control serum-treated HRGEC with and without sepiapterin and determine EC RNA expression. The PDGF/PDGFR/PI3K/Akt pathway will be targeted with pharmacologic agents or siRNA to determine the extent to which the anti-inflammatory sepiapterin effect and oxidative stress in EC are dependent upon this pathway. The ultimate goal of our translational group is to target EC dysfunction to reduce inflammation in SLE. The aims proposed here will demonstrate the most effective treatment indications, pharmacodynamic markers of response, and alternate or adjunctive targets to reduce ECD in SLE and will inform future human studies. Proposed future indications are for early prevention or adjunct induction therapy in LN and prevention of atherosclerosis in SLE.

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