The Role of Glutathione Peroxidase 4 in Regulating Glomerular Permeability in a Mouse Model of Lupus Nephritis

Abstract

Background/hypothesis of the study: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that often results in kidney damage (lupus nephritis). Glutathione peroxidase 4 (GPx4) is a key defensive player in clearing reactive oxygen species and preventing cell death using glutathione. Reductions of neutrophil GPx4 activity has recently been implicated in autoimmunity in SLE, and reduced renal expression of GPx4 was previously reported in a mouse model of SLE. Whether loss of GPx4 activity has a direct role in glomerular injury in SLE is currently unknown. Therefore, the present study aimed to investigate the role of GPx4 in regulating glomerular permeability and whether deficits in GPx4 may contribute to albuminuria in lupus nephritis. Methods and Results: Experiments utilized female (New Zealand Black x New Zealand White) F1 (NZBWF1) mice, a well-established mouse model of lupus nephritis that has a female sex bias, similar to patients. In our hands, these mice typically develop albuminuria around 34 weeks of age. Glomeruli were isolated on ice by graded sieving and underwent functional and biochemical analysis. Glomerular GPx4 expression was compared between age- and sex-matched albuminuric NZBWF1 mice (albuminuria status determined by dipstick) and healthy control New Zealand White (NZW) mice by western blot. Protein expression of GPx4 in glomeruli isolated from albuminuric 34-week-old female NZBWF1 mice was reduced to approximately 30% of the level found in NZW mice (P<0.01; n=4 mice each group). For functional analysis, glomeruli were suspended in a 5% albumin solution, and the change in volume in response to a decrease in external oncotic pressure caused by switching to a 1% albumin solution was used to determine the albumin reflection coefficient and calculate relative glomerular permeability to albumin (Palb). Experiments measured (i) Palb of glomeruli from healthy young 8-week-old NZBWF1 compared to 34-week-old albuminuric NZBWF1, and (ii) Palb of glomeruli from 8-week-old NZBWF1 mice following ex vivo treatment of glomeruli with the GPx4 inhibitor RSL3 (3μM) for 30 minutes compared to untreated glomeruli from the same mice. At least 5-8 glomeruli/mouse/treatment or age were analyzed, and the data from each mouse was averaged. As expected, 34-week-old albuminuric NZBWF1 mice showed significantly increased Palb compared with 8-week-old mice (P<0.001; n=5 mice per group). Glomeruli isolated from 8-week-old NZBWF1 mice showed increased Palb after 30 min incubation with 3μM RSL3 when compared to non-treated glomeruli (P<0.001; n=4 mice per group). Conclusion: Our data suggest that the development of albuminuria in NZBWF1 mice is associated with a reduction in glomerular expression of GPx4, and impairment of GPx4 activity can promote increased Palb. A loss of GPx4 activity may contribute to glomerular filtration barrier dysfunction and albuminuria in SLE. This work was supported by the National Institutes of Health (grant number 1R01DK119337-01A1) 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.