Estrogen hindrance escalates inflammation and neurodegeneration in the hippocampal regions of collagen-induced arthritis female Sprague-Dawley rats

Abstract

This study aims to investigate the effect of estrogen hindrance, i.e., menopause in women for instance with rheumatoid arthritis on the brain hippocampal region by using collagen-induced arthritis (CIA) female rat model (RA). CIA was induced in female rats by injecting bovine type II collagen and incomplete Freund's adjuvant. Estrogen receptor antagonist, fulvestrant (Ful), was given to RA rats to create estrogen hindrance. Control (C) and RA rats were injected with saline and DMSO, respectively, while RA + Ful rats received a 7-day fulvestrant injection. Following experiment completion, rats were sacrificed, and brains were harvested. Brains were stained with H&E and cresyl violet staining and morphological changes in the hippocampus were identified. Additionally, oxidative stress, inflammatory, and apoptosis markers' levels in the hippocampus were analyzed by qPCR, ELISA, and immunohistochemistry techniques. RA + Ful rats showed neuronal atrophy and reduced neurogenesis in the hippocampal regions. NOX4, NF-κB, IL-1β, IL-6, TNF-α, IKK-β, and Bax protein expression levels in the hippocampus were increased, whereas hippocampal Bcl-2, caspase-3, caspase-9, and IGF-1R protein expression levels were decreased. Furthermore, RA + Ful rats had lower levels of antioxidants PON-1 and catalase in the hippocampal regions. The changes in these molecular markers were statistically significant when compared to RA rats without Ful treatment (p < 0.05). Estrogen hindrance exaggerated oxidative stress, inflammation, and apoptosis which resulted in neuronal degeneration in the hippocampal regions in rheumatoid arthritis.

Keywords: Estrogen hindrance; Hippocampus; Inflammation; Neuron degeneration; Oxidative stress; Rheumatoid arthritis.