The drug disposition in the Spleen: A novel study of CYP and UGT-mediated drug metabolism

Abstract Understanding the fate of a drug, its disposition and pharmacokinetics as it reaches the site of action is key to any pharmaceutical research and development. The emerging role of the spleen in its involvement in regulating the immune system has garnered interest in new immunotherapeutic strategies. Using novel precision immunotherapeutic drugs that will potentially engage with the host immune system to specifically target and eliminate diseased cells, makes this approach a better alternative to conventional therapies. The spleen poses as a potential immunotherapeutic target and confirmation of drugs reaching its site of action requires monitoring enzymes that engages with xenobiotics like drugs. The pig was selected as the model for human based on the close homology conveyed between pig and human using a phylogenetic construction of Cytochrome P450s (CYP450) and UDP-glucuronosyltransferases (UGT) in both species. Moreover, an RNAseq transcriptome analysis between the human spleen, pig liver and spleen tissues were obtained from a next generation sequencing (NGS) to identify genes associated with drug metabolism. Immunofluorescence and Western Blot analysis was carried out to determine the protein expression of metabolizing CYP450s and UGTs in pig spleen. Therefore, drug substrates and their metabolites known in human liver were investigated in pig spleen to determine the functional expression of CYP450s and UGTs. Promising in-vitro results has demonstrated the expression of these metabolic enzymes at a functional level from observations showing elimination of drug substrates and the apparent metabolites formed. Monitoring the enzyme activities would also indicate uptake of these substrates in splenocytes, confirm that the spleen can metabolize drugs, and provide further insight into therapeutic or toxic related implications from drug interactions.