e Total parenteral nutrition (TPN) is commonly used clinically to sustain patients; however, TPN is associated with profound mucosal atrophy, which may adversely affect clinical outcomes. Using a mouse TPN model, removing enteral nutrition leads to decreased crypt proliferation, increased intestinal epithelial cell (IEC) apoptosis and increased mucosal tumor necrosis factor alpha (TNF-␣) expression that ultimately produces mucosal atrophy. Upregulation of TNF-␣ signaling plays a central role in mediating TPN-induced mucosal atrophy without intact epidermal growth factor receptor (EGFR) signaling. Currently, the mechanism and the tissue-specific contributions of TNF-␣ signaling to TPN-induced mucosal atrophy remain unclear. ADAM17 is an ectodomain sheddase that can modulate the signaling activity of several cytokine/growth factor receptor families, including the TNF-␣/TNF receptor and ErbB ligand/EGFR pathways. Using TPN-treated IEC-specific ADAM17-deficient mice, the present study demonstrates that a loss of soluble TNF-␣ signaling from IECs attenuates TPN-induced mucosal atrophy. Importantly, this response remains dependent on the maintenance of functional EGFR signaling in IECs. TNF-␣ blockade in wild-type mice receiving TPN confirmed that soluble TNF-␣ signaling is responsible for downregulation of EGFR signaling in IECs. These results demonstrate that ADAM17-mediated TNF-␣ signaling from IECs has a significant role in the development of the proinflammatory state and mucosal atrophy observed in TPN-treated mice.A lthough total parenteral nutrition (TPN) is an essential therapy for patients who cannot tolerate enteral nutrition, there are numerous and significant clinical sequelae associated with TPN treatment (1). These clinical complications, which include altered immunological responses, hepatic dysfunction, metabolic derangements, endotoxemia, bacterial infections, and sepsis, can delay or make it difficult to wean patients back onto enteral nutrition. Several studies have indicated that early TPN administration in critically ill patients is associated with worsened clinical outcomes and increased rates of septicemia, often from enterically derived organisms (1, 2). These issues clearly highlight that a more detailed understanding of the underlying mechanisms of TPN-related intestinal complications is needed both to improve the selection and administration of TPN to patients and for the development of new therapeutic options for patients dependent on TPN.The mouse model of TPN represents an ideal system to study signal transduction pathways contributing to mucosal atrophy without acute inflammatory changes or intestinal epithelial cell (IEC) destruction seen in other intestinal injury/inflammation models. The removal of enteral nutrition is associated with decreased crypt proliferation, increased IEC apoptosis, a loss of epithelial barrier function (EBF), and altered enteric microbiota, resulting in a mild proinflammatory state and mucosal atrophy (1). Previous studies have shown that upregulation of tumor...