Involvement of NF-κB in the upregulation of cystathionine-γ-lyase, a hydrogen sulfide-forming enzyme, and bladder pain accompanying cystitis in mice.

Hydrogen sulfide (H₂ S) is generated from l-cysteine by multiple enzymes including cystathionine-γ-lyase (CSE), and promotes nociception by targeting multiple molecules such as Ca_v 3.2 T-type Ca²⁺ channels. Bladder pain accompanying cyclophosphamide (CPA)-induced cystitis in mice has been shown to involve the functional upregulation of the CSE/H₂ S/Ca_v 3.2 pathway. Therefore, we investigated whether NF-κB, as an upstream signal of the CSE/H₂ S system, contributes to bladder pain in mice with CPA-induced cystitis. Bladder pain-like nociceptive behaviour was observed in CPA-treated mice, and referred hyperalgesia was evaluated by the von Frey test. Isolated bladder weights were assessed to estimate bladder swelling, and protein levels were measured by Western blotting. CPA, administered intraperitoneally, induced nociceptive behaviour, referred hyperalgesia and increased bladder weights in mice. β-Cyano-l-alanine, a reversible selective CSE inhibitor, prevented CPA-induced nociceptive behaviour, referred hyperalgesia, and, in part, increases in bladder weight. CPA markedly increased phosphorylated NF-κB p65 levels in the bladder, an effect that was prevented by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor. PDTC and curcumin, which inhibits NF-κB signals, abolished CPA-induced nociceptive behaviour, referred hyperalgesia and, in part, increases in bladder weight. CPA caused the overexpression of CSE in the bladder, and this was prevented by PDTC or curcumin. The CPA-induced activation of NF-κB signals appeared to cause CSE overexpression in the bladder, contributing to bladder pain and in part swelling, possibly through H₂ S/Ca_v 3.2 signaling. Therefore, NF-κB-inhibiting compounds including curcumin may be useful for the treatment of cystitis-related bladder pain.