| Summary: | Acute kidney injury (AKI) is a major health burden associated with a 50% mortality rate. Of particular concern, the incidence of AKI has increased dramatically over the last decade. Yet, there is a paucity of available treatments to prevent AKI or to reduce the high rate of AKI-associated mortality. A common cause of AKI, especially in hospital settings, is prolonged decreases in renal blood flow (i.e., renal ischemia). Recent studies have demonstrated that activating the cholinergic anti-inflammatory pathway via vagal stimulation can mitigate AKI severity in rodent models of renal ischemia-reperfusion (IR) injury. While vagal stimulation is not a practical approach to prevent AKI in patients due its invasive nature and numerous side effects, recent studies have identified non-neuronal cholinergic cells within the kidney that could be targeted to reduce the severity of AKI. The overarching goal of this project is to examine the potential role of the renal cholinergic system in modulating the severity of and recovery from AKI in transgenic mice expressing green fluorescent protein (GFP) under control of the choline acetyl-transferase (ChAT) promoter, a protein involved in the synthesis of acetylcholine. The objectives of this study were to develop a clinically relevant model of renal IR-induced AKI in mice by identifying the duration of ischemia required for manifestation of the effects of AKI and to determine whether differences in susceptibility to AKI exists between male and female mice. Initially, male mice underwent 20 (n=3), 22 (n=3), or 25 (n=4) minutes of bilateral renal IR under isoflurane anesthesia with body temperature controlled at 37°C. Ischemia was achieved by careful placement of vascular clamps on the renal artery and vein supplying each kidney. The severity of AKI was determined by measuring serum creatinine (SCr) at 3 days post-AKI. Compared to SCr of mice that were 3 days post-sham AKI (SCr = 0.47 mg/dl, n=2), SCr of male mice from all three ischemia time categories was substantially elevated (SCr > 3 mg/dl, n=10). However, mortality associated with 22 and 25 minutes IR was striking (>90%) making studies of long-term AKI effects difficult. In contrast, 20 minutes IR resulted in AKI manifest by elevated SCr (3.43±0.7 mg/dl, n=3), widespread acute tubular necrosis and a clinically relevant mortality rate of 50%. Next, male (n=10) and female (n=5) mice were subjected to 20 minutes of IR. The mortality rate in male mice (n=10) was 50% (n=10) through 7 days post-AKI; however, all female mice survived. Additional studies showed that female mice had lower SCr 3 days post-AKI (0.63±0.1 mg/dl, n=2) with very modest levels of acute tubular necrosis as compared to the higher SCr (1.92±0.1 mg/dl, n=2) and extensive acute tubular necrosis observed in male mice. The differences observed in AKI severity and mortality rates suggest that female mice are protected against AKI as compared to male mice and future studies will explore the potential role of the renal cholinergic system in contributing to these sex differences in AKI.
|
|---|
