Supplementary Material for: Cyclosporine A Induces MicroRNAs Controlling Innate Immunity during Renal Bacterial Infection

Urinary tract infections (UTIs) mainly due to uropathogenic Escherichia coli
(UPEC) are one of the most frequent complications in
kidney-transplanted patients, causing significant morbidity. However,
the mechanisms underlying UTI in renal grafts remain poorly understood.
Here, we analysed the effects of the potent immunosuppressive agent
cyclosporine A (CsA) on the activation of collecting duct cells that
represent a preferential site of adhesion and translocation for UPEC.
CsA induced the inhibition of lipopolysaccharide- induced activation of
collecting duct cells due to the downregulation of the expression of
TLR4 via the microRNA Let-7i. Using an experimental model of ascending
UTI, we showed that the pretreatment of mice with CsA prior to infection
induced a marked fall in cytokine production by collecting duct cells,
neutrophil recruitment, and a dramatic rise of bacterial load, but not
in infected TLR4-defective mice kidneys. This effect was also observed
in CsA-treated infected kidneys, where the expression of Let-7i was
increased. Treatment with a synthetic Let-7i mimic reproduced the
effects of CsA. Conversely, pretreatment with an anti-Let-7i antagonised
the effects of CsA and rescued the innate immune response of collecting
duct cells against UPEC. Thus, the utilisation of an anti-Let-7i during
kidney transplantation may protect CsA-treated patients from ascending
bacterial infection.