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Abstract: TH-PO535

Integrin β6 Regulates Tubuloglomerular Feedback Through the NKCC2-COX2/nNOS Pathway

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

  • Zhong, Jianyong, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Yang, Haichun, Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Fogo, Agnes B., Vanderbilt University Medical Center, Nashville, Tennessee, United States
Background

Integrin β6 (β6) is a protein expressed in some tubules and macula densa cells, which activates transforming growth factor-β (TGF-β). Our previous studies showed that β6-/- mice exhibit milder tubulointerstitial fibrosis but more severe glomerulosclerosis than wild type (WT) after 5/6 nephrectomy. This study aimed to explore the involvement of macula densa integrin β6 in the dysfunction of tubuloglomerular feedback.

Methods

We first knocked down β6 in mouse macula densa cells (MMDD1) and exposed them to high salt. The expression of Oxidative Stress Responsive Kinase 1 (OXSR1), a regulator of NKCC2 activity, was assessed by qPCR. The protein expressions of NKCC2, COX2, and nNOS were analyzed by western blot. We then measured renal clearance before and after acute volume expansion in β6-/- and WT mice.

Results

Immunostaining showed that integrin β6 and NKCC2 colocalized on the cell membrane of MMDD1. Knockdown of β6 significantly increased the expression of OXSR1 and NKCC2 and induced more nNOS and less COX2 compared to WT cells. High salt reduced COX2 and increased nNOS protein expression in WT, which was not changed in β6 knockdown cells. In vivo, following acute volume expansion with 3% of body weight volume of isotonic saline over 5 min, blood pressure decreased minimally and similarly in both groups at 15 min and recovered to the baseline level at 30 min after volume expansion. GFR of WT mice increased at 30 minutes and returned to baseline at 90 min. In contrast, integrin β6 knockout mice reached peak GFR at 60 min, but ultimately returned to baseline at 90 min.

Conclusion

These findings suggest that integrin β6 regulates tubuloglomerular feedback through the NKCC2-COX2/nNOS pathway. The dysfunction of tubuloglomerular feedback induced by β6 knockout on macula densa cells may contribute to the observed mismatch in tubulointerstitial fibrosis and glomerulosclerosis in β6-/- mice after 5/6 nephrectomy.

Funding

  • NIDDK Support