Innate immunity activation involved in unprotected porcine auto-transplant kidneys preserved by naked caspase-3 siRNA

BACKGROUND: The naked caspase-3 small interfering RNA (siRNA) infused into the renal artery during cold preservation was effective, but did not protect auto-transplant porcine kidneys with increased inflammation and apoptosis in our previous study. The mechanisms involved, in particular, whether siRNA or complementary systemic feedback eliciting innate immune responses are worthy to be further investigated. METHODS: The protein and mRNA expression of innate immunity-related molecules were detected by western blotting and quantitative PCR in the tissues previously collected from 48 h auto-transplant kidneys. The donor kidneys were retrieved from mini pigs and cold preserved by University of Wisconsin solution with/without 0.3 mg caspase-3 siRNA for 24 h. RESULTS: The protein level of Toll like receptor (TLR) 3, TLR7, and their main adapters, TRIF and MyD88, was up-regulated in the siRNA preserved auto-transplant kidneys. The mRNA level of NF-κB and c-Jun was increased, as well as pro-inflammatory cytokines, including IL-1β, IL-6, TNF-α and interferon (IFN)-α, β and γ. In addition, the non-TLR RNA sensor PKR protein, but not RIG1, was also increased in the siRNA preserved auto-transplant kidneys. CONCLUSIONS: The activation of innate immunity with amplified inflammatory responses in the caspase-3 siRNA preserved auto-transplant kidneys are associated with increased TLR3, TLR7 and PKR, which might be due to complementary systemic feedback, although persistent actions initiated by short-acting caspase-3 siRNA cannot be completely ruled out. These results provided valuable evidence to guide future siRNA design and pre-clinic studies.