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Abstract: SA-OR015

Tamm-Horsfall Protein (Uromodulin) Inhibits Systemic Oxidative Stress by Inactivating the TRPM2 Channel

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • LaFavers, Kaice A., Indiana University School of Medicine, Indianapolis, IN, Indiana, United States
  • Khan, Shehnaz, Indina university of school of medicine Nephrology, Indianapolis, Indiana, United States
  • Winfree, Seth, Indiana University School of Medicine, Indianapolis, IN, Indiana, United States
  • Hato, Takashi, Indiana University, Indianapolis, Indiana, United States
  • Dagher, Pierre C., Indiana University, Indianapolis, Indiana, United States
  • El-Achkar, Tarek M., Indiana University, Indianapolis, Indiana, United States
  • Micanovic, Radmila, Indiana University School of Medicine, Indianapolis, IN, Indiana, United States
Background

Tamm-Horsfall protein (THP) is produced exclusively in the thick ascending limb (TAL) of the loop of Henley. In TAL cells, THP is secreted apically in the urine but also released basolaterally in the interstitium and circulation. We previously showed that THP downregulates inflammatory signaling in S3 proximal tubules. Here, we investigate potential targets of THP on these cells and the role of systemically released THP.

Methods

We used THP+/+ and THP -/- mice. Various assays and technologies as described in results

Results

We performed laser microdissection on S3 and TAL tubules for transcriptomic studies. Bioinformatic analysis determined that, in the setting of THP deficiency, JNK stress kinase signaling is activated in S3 segments but not in TAL. JNK activation uniquely in S3 segments was confirmed by 3D tissue cytometry. Additional proteomic studies on S3 segments and human proximal tubular cell suggested that THP inhibits oxidative stress and Rac-1 activity, both known to be upstream of JNK. This was confirmed in vivo using intravital imaging and other measures of oxidative stress. Furthermore, we observed that THP deficiency increased oxidative injury not only in the kidney, but also systemically and in distant organs, such as the lungs. Since TRPM2, a nonvoltage activated nonselective cationic channel, is implicated in regulating oxidative stress, we investigated if THP modulates its activity. Indeed, TRPM2 is expressed in the kidney, lungs and other organs. In HEK-293 recombinant cells with inducible TRPM2, we show that THP specifically inhibits TRPM2 dependent calcium influx in a dose dependent manner. Furthermore, pharmacological inhibition of TRPM2 in THP-/- mice reduced systemic oxidative damage.

Conclusion

We show that THP inhibits oxidative stress not only in the kidney but also systemically in other organs. This effect is likely mediated through the circulating form of THP. Our data suggest that this effect, in part, is due to inhibition of the TRPM2 channel, which in some tissue types, conditions and experimental models, is known to cause downstream oxidant injury. These findings underscore the importance of THP in mediating a systemic cross-talk between the kidney and other organs and identify, for the first time, a molecular target for circulating THP.

Funding

  • NIDDK Support