[Effect of moxibustion on bladder fibrosis, oxidative stress and ferroptosis in rats with urinary retention due to spinal cord injury].

OBJECTIVES

To observe the effect of moxibustion on levels of oxidative stress- and ferroptosis-related proteins in the bladder tissues, and bladder fibrosis in rats with spinal cord injury (SCI)-induced urinary retention, so as to explore its mechanisms underlying improvement of bladder function.

METHODS

Female Wistar rats were randomly divided into normal control, sham operation, SCI model and moxibustion groups, with 12 rats in each group. The modified Allen's vertical percussion method was used to establish the model of SCI-induced urinary retention. The rats of the moxibustion group received moxibustion stimulation at "Guanyuan" (CV4) and "Zhongji"(CV3) for 20 min, once a day for 14 days. The bladder function was detected by using a urodynamic analyzer, and the motor function was detected by Basso-Beattie-Bresnahan (BBB) rating scale. After 14 days of intervention, the bladder tissue was collected for observing morphological changes by using HE staining, the interfascicular collagen deposition by using Masson staining, the mitochondrial structure by using electron microscopy, and for detecting the expression levels of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), glutathione peroxidase 4 (GPX4), collagen Ⅰ and collagen Ⅲ by Western blot. The contents of interleukin-1β (IL-1β) and reactive oxygen species (ROS) in serum were detected by ELISA. The contents of ferrous ion (Fe2+) in serum and glutathione (GSH) and malondialdehyde (MDA) in the bladder tissue were detected by colorimetric method.

RESULTS

No significant differences were found between the normal control and sham operation groups in all the indexes. Compared with the sham operation group, the BBB score, GSH content and the expression levels of Nrf2, HO-1 and GPX4 proteins in the bladder tissue were significantly decreased (P<0.01), while the bladder capacity, urinary leakage point pressure and bladder compliance, extracellular matrix (ECM) deposition and expression of collagen Ⅰ and Ⅲ in the bladder tissue, and the contents of Fe2+, ROS, IL-1β in serum and MDA in the bladder tissue were significantly increased (P<0.01) in the model group. In comparison with the model group, both the increase of the bladder capacity, urinary leakage point pressure and bladder compliance, ECM deposition and expression of collagen Ⅰ and Ⅲ, and the contents of Fe2+, ROS and IL-1β, and the decrease of the BBB score, GSH content and the expression levels of Nrf2, HO-1 and GPX4 proteins after modeling were reversed in the moxibustion group (P<0.01). Morphological observations (HE and Masson staining and electron microscope) showed disordered arrangement of muscle fibers and muscle bundles, enlargement of muscle fascicle space, atrophy, severe deposition of ECM, increase of collagen fibers, ferroptosis mitochondrial atrophy, reduction or even disappearance of mitochondrial crests, and increase of membrane density in the bladder tissue of the model group, which was relatively lighter in the injury severity in the moxibustion group.

CONCLUSIONS

Moxibustion stimulation of CV3 and CV4 can improve functional activities of the bladder in SCI-induced urinary retention rats, which may be related to its functions in inhibiting the occurrence of oxidative stress and ferroptosis, and delaying the progression of bladder fibrosis.