Identification of Cytoprotective Small Molecule Inducers of Heme Oxygenase-1

Acute kidney injury (AKI) is a major public health concern with significant attributable morbidity and mortality with no current FDA approved treatments other than supportive care through dialysis. Several pre-clinical studies have suggested that heme-oxygenase-1 (HO-1), an enzyme that catalyzes the breakdown of heme, has promise as a potential therapeutic target for AKI. Clinical trials involving HO-1 products (biliverdin, carbon monoxide, and iron), however, have not progressed beyond the Phase 1/2 level. We have identified small molecule inducers of HO-1 that enable us to exploit the full therapeutic potential of HO-1, the combination of its products, and as-yet-undefined effects of the enzyme system. Through cell-based, high throughput screens for induction of HO-1 through the human HO-1 promoter/enhancer, we identified two novel small molecules and broxaldine, an FDA approved antiprotozoal, for further consideration as candidate compounds exhibiting Emax = 70% of 5 µM hemin and EC50<10 µM. RNA sequencing identified shared binding motifs to NRF-2, a transcription factor known to regulate antioxidant genes, including HO-1. siRNA knockdown of NRF-2 confirmed the role of NRF-2 in induction of HO-1. In vitro, cytoprotective function of the candidates was assessed against cisplatin-induced cytotoxicity and apoptosis. In vivo, delivery of candidate compounds induced HO-1 expression in the kidneys of mice. This study serves as the basis for further development of small molecule HO-1 inducers as preventative or therapeutic interventions for a variety of pathologies, including AKI. Overall design: Bulk RNA sequencing of HEK293 cells treated with small molecules SRI-37618, SRI-40109, broxaldine, hemin, or DMSO (vehicle) for 4 or 8 hours. N=2 per timepoint and condition.