[Effect of Yiyuan moxibustion on regulating ferroptosis in rats with urinary retention after spinal cord injury via the NRF2/GPX4 pathway].

OBJECTIVES

To investigate the mechanism of Yiyuan moxibustion in improving lipid peroxidation and urine retention in spinal cord injury (SCI) rats by regulating ferroptosis via the nuclear factor erythroid 2-related factor 2 (NRF2)/glutathione peroxidase 4 (GPX4) pathway.

METHODS

Forty-eight female Wistar rats were randomly divided into sham operation, model, moxibustion and moxibustion + inhibitor (combination) groups, with 12 rats in each group. SCI induced urinary retention model was established by using Allen's method. Moxibustion was applied to "Shenque" (CV8), "Guanyuan"(CV4) and "Zhongji" (CV3) for 15 min, once daily for 14 d. Rats in the combination group received moxibustion combined with intraperitoneal injection of the NRF2 inhibitor ML385 (30 mg/kg) once daily for 14 consecutive days. Urodynamic analysis was used to record bladder leak point pressure, maximum bladder volume, and bladder compliance to evaluate bladder function. H.E. staining was used to observe morphological changes in spinal cord tissue. Prussian blue staining was used to observe iron deposition in spinal cord tissue. Transmission electron microscopy (TEM) was used to observe mitochondrial morphological changes in spinal cord tissue. Colorimetric assays were used to measure serum Fe2+, malondialdehyde (MDA), and reduced glutathione (GSH) levels. Western blot was used to detect the protein expressions of NRF2, GPX4, and solute carrier family 7 member 11 (SLC7A11) in spinal cord tissue.

RESULTS

Rats in the model group had disrupted spinal architecture, vacuolated neurons, swollen mitochondria with lost cristae, and brownish iron deposits, which were relatively milder in the moxibustion group. Compared with the sham operation group, the bladder leak point pressure, serum GSH content, and expression levels of NRF2, SLC7A11, and GPX4 proteins in spinal cord tissue were all significantly reduced (P<0.01), while the maximum bladder volume and bladder compliance, as well as the serum contents of Fe2+ and MDA, were significantly increased (P<0.01) in the model group. When compared to the model group and the combination group, the moxibustion group exhibited a decrease in maximum bladder volume, bladder compliance, serum Fe2+ and MDA content (P<0.01), but an increase in bladder leak point pressure, GSH content, and the expression of NRF2, SLC7A11, and GPX4 proteins (P<0.01, P<0.05).

CONCLUSIONS

Yiyuan moxibustion may alleviate lipid peroxidation caused by ferroptosis in spinal neurons by up-regulating the NRF2/GPX4 pathway, thereby promoting the recovery of neural regulation of bladder function and improving urine retention in SCI rats.