Diclofenac Immune-Mediated Hepatitis: Identification of Innate and Adaptive Immune Responses at Clinically Relevant Doses

Diclofenac is an effective medication for pain and inflammation. However, its use has been linked to hepatitis. To gain insight into diclofenac's ability to cause hepatitis, we investigated the regulation of major effectors of the immune system following daily treatment of minipigs at 3 and 15 mg/kg for 28 days. Histopathology evidenced lobular inflammation, and through a combination of immunogenomics and immunopathology, we detected marked innate and adaptive immune responses. We identified 109 significantly regulated genes linked to neutrophil, monocyte, Kupffer cell, and lymphocyte responses and 32 code for cytokine- and interferon-γ-signaling. In support of wound repair, immunopathology evidenced manifest upregulation of macrophage migration inhibitory factor and CD74. Furthermore, the strong expression of IgG and IgM underscored humoral immune responses. Diclofenac caused an activation of the complement system, especially the C1 inhibitor of the classical pathway and C3 with critical functions in liver regeneration. The marked expression of complement factor B and H of the alternate pathway modulated B-cell responses. Likely, the upregulation of factor H protected hepatocytes from injury by limiting complement-mediated damage of inflamed cells. Additionally, diclofenac treatment elicited marked hepatic expression of lysozyme and KLF6. The latter earmarks M1-polarized Kupffer cells. We observed an extraordinary induction of calprotectin/S100A9 and of the monocyte/macrophage CD163 scavenger receptor, and therefore, we detected innate immune sensing of damaged cells. Lastly, we noted an unprecedented induction of the acute phase reactant SAA1 and DEC-205, which recognize apoptotic and necrotic cells. Together, our results offer mechanistic insights into immune-mediated liver injury patterns following diclofenac treatment.