Involvement of Interleukin-6-Regulated Nitric Oxide Synthase in Hemorrhagic Cystitis and Impaired Bladder Contractions in Young Rats Induced by Acrolein, a Urinary Metabolite of Cyclophosphamide

Abstract

Hemorrhagic cystitis is a common complication in children receiving cyclophosphamide, a chemotherapeutic alkylating agent. Acrolein is a urinary metabolite from cyclophosphamide and can induce hemorrhagic cystitis. Here, we investigated the effects and mechanisms of acrolein by intravesical instillation on urinary bladder muscle contractions and pathological alterations in rats. Acrolein instillation significantly increased the muscle contractions of rat bladder detrusor after 1 and 6 h but markedly decreased detrusor contractions after 24 h. Acrolein increased phosphorylated protein kinase C (pan-PKC) expressions in bladders after 1 and 6 h but inhibited it after 24 h. Inducible nitric oxide (NO) synthase (iNOS) protein expressions were markedly induced in bladders 24 h after acrolein treatment. Twenty-four-hour acrolein instillation increased the levels of nitrite/nitrate and interleukin-6 (IL-6) in the urinary bladder. The iNOS inhibitors significantly inhibited the acrolein-increased nitrite/nitrate levels, but not IL-6 levels. IL-6-neutralizing antibodies effectively inhibited the acrolein-increased NOx levels. The increased detrusor contractions by 1-h acrolein treatment were significantly reversed by the PKC inhibitor RO32-0432, and the decreased detrusor contractions by 24-h acrolein treatment were significantly reversed by the iNOS inhibitor and IL-6-neutralizing antibody. Both the iNOS inhibitor and IL-6-neutralizing antibody effectively reversed the increased iNOS expression, decreased PKC phosphorylation, increased bladder weight, and hemorrhagic cystitis in rats 24 h after acrolein treatment. Taken together, these results suggest that an IL-6-regulated iNOS/NO signaling pathway participates in the acrolein-triggered detrusor contraction inhibition and hemorrhagic cystitis. These findings may help us to find a new strategy to treat cyclophosphamide-induced hemorrhagic cystitis.