Neuregulin-1-ErbB signaling promotes microglia activation contributing to mechanical allodynia of cyclophosphamide-induced cystitis.

AIMS: Central sensitization playsimportant roles in cyclophosphamide (CYP)-induced cystitis. In addition, as a visceral pain, CYP-induced chronic pain shares common pathophysiological mechanisms with neuropathic pain. Previous studies demonstrated that neuregulin-1 (Nrg1)-ErbB signaling contributes to neuropathic pain, but whether and how this signaling influences mechanical allodynia in CYP-induced cystitis is unclear. This study aimed to determine whether and how Nrg1-ErbB signaling modulates mechanical allodynia in a CYP-induced cystitis rat model. METHODS: Systemic injection with CYP was used to establish a rat model of bladder pain syndrome/interstitial cystitis (BPS/IC). An irreversible ErbB family receptor inhibitor, PD168393, and exogenous Nrg1 were intrathecally injected to modulate Nrg1-ErbB signaling. Mechanical allodynia in the lower abdomen was assessed with von-Frey filaments using the up-down method. Western blot analysis and immunofluorescence staining were used to measure the expression of Nrg1-ErbB signaling, Iba-1, p-p38, and IL-1ß in the L6-S1 spinal dorsal horn (SDH). RESULTS: We observed upregulation of Nrg1-ErbB signaling as well as overexpression of the microglia activation markers Iba-1 and p-p38 and the proinflammatory factor, interleukin-1ß (IL-1ß), in the SDH of the cystitis group. Further, treatment with PD168393 attenuated mechanical allodynia in CYP-induced cystitis and inhibited microglia activation, leading to decreased production of IL-1ß. The inhibitor PD168393 reversed the algesic effect of exogenous Nrg1 on the cystitis model. CONCLUSIONS: Nrg1-ErbB signaling may promote microglia activation, contributing to mechanical allodynia of CYP-induced cystitis. Our study showed that modulation of Nrg1-ErbB signaling may have therapeutic value for treating pain symptoms in BPS/IC.