# Heme-mediated Mitochondrial Injury, Senescence, Acute Kidney Injury and Chronic Kidney Disease

> **NIH NIH R01** · MAYO CLINIC ROCHESTER · 2024 · $575,207

## Abstract

PROJECT SUMMARY
Senescent cells (SCs) cause senescence, a dominant risk factor for acute kidney injury (AKI). SCs are cell
cycle-arrested (due to upregulated cell cycle inhibitors p16Ink4a and p21Cip1) and display a senescence-
associated secretory phenotype (SASP) which is proinflammatory and proapoptotic. Senolytics, agents that kill
SCs, are now in clinical trials. We demonstrate senescence in the heme protein-mediated AKI model (HP-AKI)
as indicated by multiple indices. The significance of such changes – injurious or protective – is unknown as
regards AKI. The AKI field recognizes that mitochondrial injury drives AKI, while the senescence field
recognizes that mitochondrial injury elicits senescence; this application uniquely unites these two concepts.
Early in HP-AKI, we demonstrate that mitochondria are injured and their heme content increased; normal
mitochondria, exposed to such heme content, cease functioning. Heme, a prooxidant tetrapyrrole, present in
the ubiquitous family of heme proteins, is freed when heme proteins are destabilized because of cellular stress.
We also demonstrate that heme induces p16Ink4a/p21Cip1 and a SASP, and suppresses PGC-1α. In exploring
heme-induced mitochondrial injury and induction of p16Ink4a/p21Cip1, we focused on two transcription factors
both upregulated by mitochondrial injury, one, ETS1, being an inducer of p16Ink4a, the other, ATF4, an inducer
of p21Cip1. Our preliminary data demonstrate that these 4 principal molecules (ETS1, ATF4, p16Ink4a, p21Cip1)
are all induced in HP-AKI; in heme-exposed renal proximal tubular epithelial cells in vitro; and in renal
ischemia-reperfusion injury (IRI). Our hypothesis is that AKI results from heme-mediated mitochondrial injury
and ensuing senescence, a thesis to be tested in three aims. Aim I: Define the role of heme-mediated
mitochondrial injury in ETS1 and ATF4 expression, senescence, and AKI. Using complementary in vivo
and in vitro approaches, we will sequentially examine the role of heme-mediated mitochondrial injury; the
contribution of ETS1, ATF4, and ETS1/ATF4-independent pathways; and the involvement of senescence in
AKI. Aim II: Define the roles of p21Cip1 and p16Ink4a in AKI: Genetic strategies. The role of p21Cip1 in AKI will
be examined by inducible deletion of high p21Cip1-expressing cells and with proximal tubule-specific p21 KO
mice. The role of p16Ink4a will be examined by inducible deletion of high p16Ink4a-expressing cells and by
inducible proximal tubule-specific deletion of high p16Ink4a-expressing cells. Aim III: Define the effect of
senolytics in AKI. SCs survive because of upregulated anti-apoptotic pathways, while senolytics kill SCs but
not non-SCs. This aim examines the efficacy of senolytics in AKI, and in reducing the sensitivity of aged mice
to AKI. In sum, this resubmitted R01 examines senescence in AKI, linking it sequentially to heme-mediated
mitochondrial injury, the transcription factors ETS1 and ATF4, and p16Ink4a and p21Cip1. T...

## Key facts

- **NIH application ID:** 10805459
- **Project number:** 5R01DK133401-02
- **Recipient organization:** MAYO CLINIC ROCHESTER
- **Principal Investigator:** KARL A. NATH
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $575,207
- **Award type:** 5
- **Project period:** 2023-03-15 → 2027-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10805459

## Citation

> US National Institutes of Health, RePORTER application 10805459, Heme-mediated Mitochondrial Injury, Senescence, Acute Kidney Injury and Chronic Kidney Disease (5R01DK133401-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10805459. Licensed CC0.

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