Nod1 and Nod2 Are Expressed in Human and Murine Renal Tubular Epithelial Cells and Participate in Renal Ischemia Reperfusion Injury

Nucleotide-binding oligomerization domain (Nod) 1 and Nod2 are members of a family of intracellular innate sensors that participate in innate immune responses to pathogens and molecules released during the course of tissue injury, including injury induced by ischemia. Ischemic injury to the kidney is characterized by renal tubular epithelial apoptosis and inflammation. Among the best studied intracellular innate immune receptors known to contribute to apoptosis and inflammation are Nod1 and Nod2. Our study compared and contrasted the effects of renal ischemia in wild-type mice and mice deficient in Nod1, Nod2, Nod(1 x 2), and in their downstream signaling molecule receptor-interacting protein 2. We found that Nod1 and Nod2 were present in renal tubular epithelial cells in both mouse and human kidneys and that the absence of these receptors in mice resulted in protection from kidney ischemia reperfusion injury. Significant protection from kidney injury was seen with a deficiency of Nod2 and receptor-interacting protein 2, and the simultaneous deficiency of Nod1 and Nod2 provided even greater protection. We conclude that the intracellular sensors Nod1 and Nod2 play an important role in the pathogenesis of acute ischemic injury of the kidney, although possibly through different mechanisms.