Hyperglycemia Induces Remodeling of Nitric Oxide Synthase Activity in Glomerular Podocytes
Authors: Stefanenko Mariia , Fedoriuk Mykhailo , Semenikhina Marharyta , Stadler Krisztian , Russell Dayvia A , Lipschutz Joshua , Staruschenko Alexander 
Published: May 2024

Background: The regulation of glomerular filtration is influenced by the renin-angiotensin system (RAS) and the release of nitric oxide (NO) by glomerular cells. Several studies suggest that NO levels in glomeruli decrease as renal pathology develops, and restoring NO levels can be beneficial for glomerular function. Despite these findings, the expression of nitric oxide synthase (NOS) subunits in podocytes, particularly under pathological conditions, still requires further investigation. We hypothesized that decreased NO bioavailability in diabetes and hyperglycemia is linked to pathological NOS remodeling, thus influencing redox balance in podocytes and promoting renal damage. Methods: Live-cell confocal imaging was used to investigate NO production and the distribution of NOS in both control and hyperglycemic conditions. First, we used immortalized human podocytes (obtained from M. Saleem lab) loaded with the DAF-FM fluorescent marker in control and hyperglycemic (exposed to high glucose for 12 hours) conditions. Next, freshly isolated glomeruli from Type 2 Diabetic Nephropathy (T2DN) and Wistar male rats (age 26-30 weeks) were used to confirm our data ex vivo. NO production was monitored following Angiotensin II (Ang II) stimulation, and the distribution of NOS was determined using specific NOS1 and NOS2 commercially available inhibitors (Nω-Propyl-L-arginine hydrochloride and L-NIL, respectively). One-way ANOVA (OriginPro) was used for statistical analysis. Results: Upon application of Ang II, rapid NO production was observed in cultured and Wistar rats isolated glomeruli podocytes. The release of NO was blocked by preincubation with corresponding inhibitors targeting NOS. Our findings reveal that NOS1 primarily contributes to signaling in healthy podocytes, accounting for 69±5% of the total NO response, while the remaining NO production mediated by the RAS is attributed to NOS2 (39±5%). In diabetic conditions, the maximal amplitude of NO production mediated by Ang II was decreased by 22±10% compared to the control (one-way ANOVA, n≥24, p<0.001). Furthermore, high glucose conditions significantly altered NOS distribution in podocytes, where NOS2 signaling became predominant (89±7% of the total NO response), and the contribution of NOS1 became less significant. Conclusions: The changes in the distribution of NO sources could be associated with heightened oxidative and nitrosative stress, promoting renal damage. Our research demonstrates that in diabetes, NOS2 activity becomes predominant, potentially playing a direct role in advancing pathological processes in podocytes. Revealing the mechanisms of this fundamental pathway in the glomerulus impacts our progress toward new treatment and preventive measures for diabetic kidney disease development. This research was supported by National Institutes of Health Grants R01 DK126720 (to OP), R01 DK129227 (to AS and OP), and R01 DK115749 (to KS), US Department of Veteran Affairs grants I01CX002391 (to JHL), I01CX001248 (JCO) and I01 BX004024 (to AS). This is the full abstract presented at the American Physiology Summit 2024 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.