Kidney Week

Abstract: FR-PO067

Identifying the Target of Pro-Regenerative Compound, PTBA, to Improve Post-AKI Repair

Session Information

• AKI: Tubules, Metabolism, New Models
  October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Han, Hwa In, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Hwa In Han,

• Crunk, Amanda, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Amanda Crunk,

• Hukriede, Neil A., University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Neil A. Hukriede,

Background

Despite the high prevalence of AKI, no approved therapeutic directly repairs renal tubular epithelial cells (RTEC). We discovered a small molecule, phenyl-thio butanoic acid (PTBA), which improves post-AKI survival, RTEC dedifferentiation & proliferation, & attenuates fibrosis in various models of AKI. In vitro studies suggest histone deacetylase 8 (HDAC8) as a PTBA target. We utilize hdac8 mutant zebrafish to investigate loss-of-function in a nephrotoxin model of AKI. HDAC8 deacetylates structural maintenance of chromosomes 3 (SMC3), a subunit of cohesin involved in sister chromatid cohesion & subsequent segregation. Without HDAC8, there is a perturbance of SMC3 acetylation resulting in G1/S delay. G1/S arrest has been reported as a protective mechanism to allow RTEC proliferation, while G2/M arrest produces pro-fibrotic factors. We hypothesize HDAC8 inhibition dysregulates the SMC3 acetylation cycle, thereby promoting G1/S delay rather than G2/M arrest in RTECs, acting as a protective mechanism.

Methods

We utilized hdac8 null mutant fish to investigate changes in the repair response. To analyze injury response at a cellular level, we utilized immunohistochemistry to characterize cell cycle phases: EdU (S), PCNA (S), & Phospho-Histone H3 (pH3) (G2/M). We compared Smc3^Ac changes, a potential downstream target of Hdac8, in wild types & hdac8^-/- by western blot & profiled the acetylome in wildtype, mutant, & compound treated zebrafish larvae.

Results

Upon gentamicin induced AKI, hdac8^-/- fish exhibited increased survival as compared to genetically wildtype larvae. In assessing cell cycle changes, we identified an increased number of PCNA+ & EdU+ RTECs in hdac8^-/-. However, hdac8^-/- showed a lower number of pH3+ RTECs, a marker of G2/M. Upon investigating SMC3^Ac levels, we observed increased SMC3^Ac in hdac8^-/- larvae.

Conclusion

HDAC8 inhibition & SMC3 acetylation is a potential mechanism for increasing post-AKI repair. Genetic ablation of hdac8 shows enhanced post-AKI survival. Cell cycle analysis suggests absence of Hdac8 activity increases PCNA & EdU, S-phase markers, while lowering G2/M arrest. This increase in S phase & decrease in G2/M may be attributed to the lack of interaction between Hdac8 & Smc3. Overall, we identified a target for HDAC8 & SMC3 as a potential molecular pathway for RTECs to prefer G1/S delay, rather than G2/M as a protective mechanism during AKI.

Funding

• NIDDK Support