Targeting inflammation and oxidative stress in experimental colitis through IL-6 siRNA and ascorbic acid co-loaded trimethyl chitosan nanoparticles

Using short interfering RNA (siRNA) to reduce the overexpression of pro-inflammatory cytokines associated with colitis proved effective, but co-administration with an antioxidant could significantly enhance therapeutic outcomes. The objective of this study was to develop a colon-targeted interleukin-6 (IL-6) siRNA and ascorbic acid (AA)-loaded polymeric nanoparticulate system (siRNA_AA NPs) and to investigate whether it can attenuate inflammation through synergistic anti-inflammatory and antioxidant effect in an experimental model of induced colitis. Trimethyl chitosan (TMC) nanoparticles (NPs) were prepared and characterized, and the influence of different formulation factors on their quality characteristics was evaluated, in order to select the most promising formulation to be tested in a model of colitis induced in mice. CD1 mice (n = 36) were divided into six groups. After induction of colitis, groups were treated by oral gavage with saline solution (healthy and disease control), prednisolone (reference), siRNA NPs (reference), scramble_AA NPs (reference), and siRNA_AA NPs (test). siRNA_AA NPs proved to be effective in the treatment of induced colitis, showing the most significant gene silencing of IL-6 and IL-1β as confirmed by PCR analysis. This silencing effect surpassed that observed with the reference treatment, prednisolone. Histopathological analysis indicated the ability of siRNA_AA NPs to induce repair processes of tissue damage, thus confirming the study hypothesis. The results obtained provide an important contribution regarding the effects obtained through combined targeting of the most important pathophysiological mechanisms involved in colitis, by simultaneous administration of antioxidants and nucleic acids inhibiting inflammatory cytokines.