Acute kidney injury (AKI) is a major complication for hospitalized patients, and renal ischemia is a predominant risk factor. Intensive research into mechanisms underlying renal dysfunction following ischemia have not translated to new therapies, in part because different forms of ischemia may involve non- overlapping molecular pathways. RATIONALE: PGC-1a, a regulator of mitochondrial biogenesis, is heavily expressed in the proximal tubule, becomes suppressed early during sepsis and ischemia-reperfusion injury, and in both situations, exacerbates renal function when genetically deleted from the proximal tubule. Human proximal tubular cells respond to inflammatory mediators by suppressing downstream effectors of PGC-1a and diminishing oxygen consumption, changes reversed by forced expression of PGC-1a. HYPOTHESIS: This proposal will test the hypothesis that suppression of PGC-1a may be a shared mechanism that exacerbates renal function in two forms of ischemic AKI, sepsis and ischemia-reperfusion injury (IRI).
AIMS :
The first aim will investigate mechanisms that enable inflammatory mediators to suppress PGC-1a expression in primary human proximal tubular cells.
The second aim will use models of sepsis and IRI in proximal tubular PGC-1a knockout mice to elucidate critical downstream effectors of PGC-1a that may be unique or shared in these two forms of AKI.
The third aim will ask whether proximal tubular induction of PGC- 1a can ameliorate these forms of AKI by applying pharmaceutical inducers in wildtype, global and tubule- specific knockout mice. RESEARCH DESIGN: The design offers loss- and gain-of-function experiments to examine upstream regulators and downstream effectors of PGC-1a. The experimental design will integrate findings across cellular and live animal experiments, imaging modalities and biochemical studies, using stringent genetic tools to address the core hypothesis.
Sepsis and ischemia-reperfusion injury are major contributors to ischemic renal injury suffered by hospitalized patients. The effect of PGC-1a in experimental models of both suggests that this molecule may participate in a general mechanism of ischemic renal injury. Understanding how PGC- 1a becomes suppressed in these settings and what effectors of PGC-1a are most critical has potential not only to advance our fundamental understanding of renal biology, but also to translate into novel therapeutic possibilities for this common and morbid disease.
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