Normalization of magnesium deficiency attenuated mechanical allodynia, depressive-like behaviors, and memory deficits associated with cyclophosphamide-induced cystitis by inhibiting TNF-α/NF-κB signaling in female rats.

BACKGROUND: Bladder-related pain symptoms in patients with bladder pain syndrome/interstitial cystitis (BPS/IC) are often accompanied by depression and memory deficits. Magnesium deficiency contributes to neuroinflammation and is associated with pain, depression, and memory deficits. Neuroinflammation is involved in the mechanical allodynia of cyclophosphamide (CYP)-induced cystitis. Magnesium-L-Threonate (L-TAMS) supplementation can attenuate neuroinflammation. This study aimed to determine whether and how L-TAMS influences mechanical allodynia and accompanying depressive symptoms and memory deficits in CYP-induced cystitis. METHODS: Injection of CYP (50 mg/kg, intraperitoneally, every 3 days for 3 doses) was used to establish a rat model of BPS/IC. L-TAMS was administered in drinking water (604 mg·kg-1·day-1). Mechanical allodynia in the lower abdomen was assessed with von Frey filaments using the up-down method. Forced swim test (FST) and sucrose preference test (SPT) were used to measure depressive-like behaviors. Novel object recognition test (NORT) was used to detect short-term memory function. Concentrations of Mg2+ in serum and cerebrospinal fluid (CSF) were measured by calmagite chronometry. Western blot and immunofluorescence staining measured the expression of tumor necrosis factor-α/nuclear factor-κB (TNF-α/NF-κB), interleukin-1ß (IL-1ß), and N-methyl-D-aspartate receptor type 2B subunit (NR2B) of the N-methyl-D-aspartate receptor in the L6-S1 spinal dorsal horn (SDH) and hippocampus. RESULTS: Free Mg2+ was reduced in the serum and CSF of the CYP-induced cystitis rats on days 8, 12, and 20 after the first CYP injection. Magnesium deficiency in the serum and CSF correlated with the mechanical withdrawal threshold, depressive-like behaviors, and short-term memory deficits (STMD). Oral application of L-TAMS prevented magnesium deficiency and attenuated mechanical allodynia (n = 14) and normalized depressive-like behaviors (n = 10) and STMD (n = 10). The upregulation of TNF-α/NF-κB signaling and IL-1ß in the L6-S1 SDH or hippocampus was reversed by L-TAMS. The change in NR2B expression in the SDH and hippocampus in the cystitis model was normalized by L-TAMS. CONCLUSIONS: Normalization of magnesium deficiency by L-TAMS attenuated mechanical allodynia, depressive-like behaviors, and STMD in the CYP-induced cystitis model via inhibition of TNF-α/NF-κВ signaling and normalization of NR2B expression. Our study provides evidence that L-TAMS may have therapeutic value for treating pain and comorbid depression or memory deficits in BPS/IC patients.

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.