ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: PO0246

Reduced Levels of Cyclic-GMP and Inhibition of cGMP-Dependent Protein Kinase Activate p21Cip1/p27Kip1 and Lead to Renal Fibrosis and Dysfunction

Session Information

  • AKI Mechanisms - 3
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Das, Subhankar, Tulane University Health Sciences Center School of Medicine, New Orleans, Louisiana, United States
  • Neelamegam, Kandasamy, Tulane University Health Sciences Center School of Medicine, New Orleans, Louisiana, United States
  • Pandey, Kailash Nath, Tulane University Health Sciences Center School of Medicine, New Orleans, Louisiana, United States
Background

Targeted-deletion of Npr1 (coding for guanylyl cyclase/natriuretic peptide receptor-A, GC-A/NPRA) exhibits hypertrophic and proliferative effects in target organs of Npr1 gene-knockout mice; however, the molecular mechanisms of these pathologies are poorly understood. Fibrosis and hypertrophy are regulated by p21Cip1 and p27Kip1, cell-cycle regulatory proteins that inhibit cyclin and cyclin-dependent kinase (cyclin-CDK) complex.

Methods

We examined the activation of CDK blocker (p21Cip1/p27Kip1) in Npr1 gene-knockout (0-copy; Npr1-/-) mice and the GC inhibitor, A71915-treated and cGMP-dependent protein kinase (cGK) inhibitor, Rp-8-Br-cGMPS (Rp)-treated wild-type 2-copy (Npr1+/+) and gene-duplicated 4-copy (Npr1++/++) mice using Western blot and quantitative real-time PCR. Systolic blood pressure (BP) was determined by non-invasive tail-cuff method.

Results

Renal cGMP levels and cGK activity were significantly decreased in 0-copy mice (p<0.0001), A71915-treated (p<0.001) and Rp-treated (p<0.05) 2-copy and 4-copy mice as compared with control animals. The results showed a high BP level in 0-copy mice (138.6 ± 3.1 mmHg; p<0.001) and significantly lower BP in 4-copy mice (86.0 ± 2.8 mmHg; p<0.01) compared to 2-copy mice (102.2 ± 1.7 mmHg). Treatment with A71915 and Rp showed significant increase in BP in 2-copy mice but only a small increase in 4-copy mice compared with untreated control animals. Increased phosphorylation of p-Erk1/2 (3-fold), p-p38MAPK (4-fold), p21Cip1 (6-fold), and p27Kip1 (5-fold) occurred in 0-copy, A71915-treated 2-copy, and A71915-treated 4-copy mice; however, Rp treatment caused minimal changes compared to controls. Proinflammatory and profibrotic cytokines, including TNF-α (6-fold), IL-6 (3-fold), and TGF-β1 (4-fold) were increased in plasma and kidney of 0-copy and A791915-treated 2-copy mice, but less in A71915-treated 4-copy mice. Renal pathology, including fibrosis, mesangial matrix expansion, and tubular hypertrophy were significantly higher in 0-copy and A71915-treated 2-copy mice but minimally in 4-copy mice compared with controls.

Conclusion

The present results suggest that Npr1 has a pivotal role in inhibiting the renal fibrosis and pathology and exerts renal protective effects through the cGMP/cGK axis by repressing the CDK inhibitors, p21Cip1 and p27Kip1.

Funding

  • Other NIH Support