Molybdenum and cadmium co-activation of TLR4/MyD88/NF-κB: the hidden driver of lymphocyte inflammation in sheep spleen.

Abstract

Environmental accumulation of excessive molybdenum (Mo) and cadmium (Cd) exerts detrimental effects on organisms. The TLR4/MyD88/NF-κB signaling cascade is classified as a core pathway responsible for regulating inflammatory responses in organisms. To elucidate the mechanism by which combined Mo and Cd exposure induces sheep spleen injury and clarify how the TLR4/MyD88/NF-κB pathway modulates this pathological process, we constructed both in vivo and in vitro models. Mo and/or Cd exposure induces splenic histological changes and mitochondrial ultrastructural damage. Notably, mRNA transcript and protein abundances of TLR4/MyD88/NF-κB pathway-related molecules and pro-inflammatory cytokines were significantly elevated in sheep splenic tissue. Concurrently, this tissue showed a marked drop in T-SOD and CAT activity, in contrast to the significant increase in MDA and H2O2 concentrations. In parallel, observations from the in vitro assay showed that single or combined treatment with Mo and Cd significantly upregulated the expression of TLR4/MyD88/NF-κB pathway-associated molecules, accompanied by elevated ROS levels and exacerbated lipid peroxidation in splenic lymphocytes. We further observed a substantial decrease in antioxidant enzyme activities, alongside a significant reduction in immunoglobulin levels in treated cells' supernatant. Importantly, application of a TLR4 inhibitor effectively mitigated the Mo- and/or Cd-induced damage to splenic lymphocytes along with associated oxidative lesions. It simultaneously inhibited ROS production, downregulated pro-inflammatory cytokine expression, and increased immunoglobulin levels in the experimental model. Collectively, our findings indicate that combined Mo and Cd exposure induces splenic inflammatory responses and oxidative stress-mediated lymphocyte injury by activating the TLR4/MyD88/NF-κB signaling cascade.