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Abstract: SA-PO994

The Urothelium Deactivates Hematuria

Session Information

  • CKD: Pathobiology - II
    November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

  • 2203 CKD (Non-Dialysis): Mechanisms

Authors

  • Shen, Tian, Columbia University, New York, New York, United States
  • Xu, Katherine, Columbia University, New York, New York, United States
  • Neupane, Uddhav, Columbia University, New York, New York, United States
  • Barasch, Jonathan M., Columbia University, New York, New York, United States
Background

American Urological Association reports that urine contains ~3 million RBC/day (“Addis Count”), containing 3x1015 heme-bound iron atoms, sufficient to cause urothelial damage and promote growth of 3x1010 bacteria. Hemolytic UTI increases uHeme by 5 fold, further promoting infection and cell damage. These data suggest that bladder expresses a heme detoxification system.

Methods

We used Hmox1 reporter mice and novel Nile Red-Palladium based probes to detect carbon monoxide (CO) with IVIS. Slc48a1 knockouts and Hmox1f/f mice were kind gifts of Iqbal Hamza (UMaryland) and Anupam Agarwal (UAlabama), respectively. We also created nascent RNA capture from urothelia using uracil phosphoribosyl transferase expression (Rosa-Uprtf/+;Upk2Cre-ERT) and 4-thiouracil pulse. RNAScope and immunostaining confirmed gene expression. Male and female mice were inoculated with 107 UPEC.

Results

Infected urothelium demonstrated the expression of heme metabolic genes (Hp, Bach1, Hmox1, Slc48a1, Hebp) and heme regulatory proteins Bmal and Npas2 within 4-6hrs of bacterial inoculation. To determine gene activity, we identified contemporaneous activation of Hmox1 and release of CO (breakdown product of heme) 4-8hrs post infection (Heme or RBC lysis were positive controls). In addition, iron disposal genes (Lcn2, lactoferrin, ferritin, Slc11a1, Slc40a1), downstream of heme metabolism were co-activated by UTI. The metabolism of heme contributed to the detachment and shedding of urothelial cells between 8-12hrs, since deletion of Slc48a1, the heme intake transporter (I.Hamza) and Hmox1, mitigated the denudation of bladder mucosa from 70% to 40% of surface area (Padj=0.02).

Conclusion

We have identified an endogenous heme metabolic pathway in urothelia that is superactivated by excess heme or UTI likely mitigating bacterial growth. However the capture of excess heme in the setting of hematuria or UTI likely contributes to urothelial death and shedding.

Funding

  • NIDDK Support