An Expandable Mechanopharmaceutical Device (2): Drug Induced Granulomas Maximize the Cargo Sequestering Capacity of Macrophages in the Liver

Abstract

Purpose: Drug-induced liver injuries (DILI) comprise a significant proportion of adverse drug reactions leading to hospitalizations and death. One frequent DILI is granulomatous inflammation from exposure to harmful metabolites that activate inflammatory pathways of immune cells of the liver, which may act as a barrier to isolate the irritating stimulus and limit tissue damage. Methods: Paralleling the accumulation of CFZ precipitates in the liver, granulomatous inflammation was studied to gain insight into its effect on liver structure and function. A structural analog that does not precipitate within macrophages was also studied using micro-analytical approaches. Depleting macrophages was used to inhibit granuloma formation and assess its effect on drug bioaccumulation and toxicity. Results: Granuloma-associated macrophages showed a distinct phenotype, differentiating them from non-granuloma macrophages. Granulomas were induced by insoluble CFZ cargo, but not by the more soluble analog, pointing to precipitation being a factor driving granulomatous inflammation. Granuloma-associated macrophages showed increased activation of lysosomal master-regulator transcription factor EB (TFEB). Inhibiting granuloma formation increased hepatic necrosis and systemic toxicity in CFZ-treated animals. Conclusions: Granuloma-associated macrophages are a specialized cell population equipped to actively sequester and stabilize cytotoxic chemotherapeutic agents. Thus, drug-induced granulomas may function as drug sequestering "organoids"-an induced, specialized subcompartment-to limit tissue damage.

Distinguishing the Concentration- vs. Bioaccumulation-Dependent Immunological and Metabolic Effects of Clofazimine

“…Post-splenectomy, the introduction of CFZ resulted in cytokine signaling consistent with M2 macrophage differentiation [ 26 , 27 , 38 , 39 ]. Prior examination of macrophage populations after CFZ dosing has shown increases in monocyte proliferation, liver granulomas, and profound splenomegaly, indicative of increased immune activity [ 14 , 40 ]. The relative increase in serum cytokine levels of the CFZ-treated splenectomy group compared to CFZ alone shows that asplenia plays a role in furthering this response.…”

“…This finding implies that the spleen modulates the magnitude of the CFZ inflammatory response, and in the absence of splenic modulation, a more profound immune response to CFZ is observed. Prior research has established massive drug accumulation in macrophages, leading to increases in the macrophage number and the formation of liver granulomas [ 5 , 11 , 14 , 40 ]. However, studies on macrophage populations and complete blood counts are an important next step in identifying a causal link between splenectomies and immune cell differentiation in the presence of CFZ.…”