Abstract P282: Knockout of Transient Receptor Potential Ankyrin 1 Exacerbates Renal Ischemia-Reperfusion Injury

Abstract

Transient receptor potential ankyrin 1 (TRPA1) is a newly identified oxidant sensor and has anti-oxidative properties. The role of TRPA1 in acute kidney injury is largely unknown. In this study, we test the hypothesis that dysfunctional TRPA1 leads to aggravated renal inflammation and injury after renal ischemia-reperfusion injury using Trpa1 gene knockout and wild-type mice. Male 8-week-old mice were subjected to renal ischemia for 30 minutes by clamping bilateral renal pedicles under isoflurane anesthesia; the mice were sacrificed at 24 hours after surgery. Renal functional impairment, tubular injury, oxidative stress, and renal inflammation were measured at 24 hours after reperfusion. TRPA1 was found to be expressed in the kidney of wild-type mice and significantly downregulated after ischemia-reperfusion injury (p<0.01). In Trpa1 knockout mice, plasma creatinine (1.58±0.08 vs. 1.19±0.07 mg/dl, p<0.01) and blood urea nitrogen (171.1±6.5 vs. 143.2±3.9 mg/dl, p<0.01) levels after ischemia-reperfusion injury were significantly higher than those in wild-type mice. Similarly, tubular injury score, calculated based on hematoxylin- and eosin-stained kidney sections, was significantly elevated in Trpa1 knockout mice compared with wild-type mice (p<0.05). Dihydroethidium-stained sections showed that superoxide production was enhanced in Trpa1 knockout mice than wild-type mice after ischemia-reperfusion injury (p<0.01). In renal injured mice, immunofluorescence staining showed that F4/80-positive macrophages were elevated in Trpa1 knockout mice than wild-type mice (p<0.01). Moreover, inflammatory cytokines, including tumor necrosis factor-alpha, interleukin-1β, and interleukin-6 in the kidneys, were increased in Trpa1 knockout mice compared to wild-type mice (all p<0.05). These results show that knockout of TRPA1 exacerbates renal oxidative stress, inflammation, and injury after ischemia-reperfusion, indicating that dysfunctional TRPA1 may lead to impaired protective mechanisms for the kidney while TRPA1 activation may serve as therapeutic means preventing renal injury.