Fine particle exposure-induced renal injury and the protective effect of multi-strain probiotics: Involvement of bitter taste transduction and inflammatory response.

Bitter taste receptors are distributed in various non-taste tissues and cells, where they exert crucial roles in neuroimmune regulation and inflammatory response. In this study, a mouse model of fine particle (FPs) exposure was established by nebulized ovalbumin (OVA) inhalation to investigate the effects of FPs on renal function and structure. The experiment results revealed that inhalation of OVA led to glomerular atrophy, and renal tubular epithelial cell swelling and vacuolization, accompanied by increased levels of blood urea nitrogen and creatinine in the bloodstream. OVA inhalation induced a significant elevation in the levels of H2O2 and malondialdehyde (MDA), while significantly decreased the activity of total superoxide dismutase (T-SOD) and the content of glutathione (GSH) in renal tissues. Furthermore, OVA downregulated Th1 cytokine IFN-γ, upregulated Th2 cytokines IL-4, IL-5 and IL-13, and activated pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) as well as genes involved in inflammatory pathways (TLR-2, TLR-4, MyD88, NF-κB, JAK-1, JAK-2, JAK-3, STAT-3, STAT-6). Notably, OVA-induced kidney injury was accompanied by the downregulation of bitter taste receptors and their downstream signaling molecules (α-gustducin, transient receptor potential melastatin 5 [Trpm5]). However, gavage administration of multi-strain probiotics significantly alleviated the toxic effects of OVA on the mouse kidneys, as evidenced by the reversal of the aforementioned abnormal changes in renal structure, biochemical indicators, oxidative stress markers, inflammatory factors, and bitter taste transduction-related molecules. Collectively, these findings indicate that OVA-induced distal organ injury, particularly renal injury, is associated with systemic inflammation and the inhibition of bitter taste transduction pathways. The protective effect of multi-strain probiotics on OVA-inhaled mice is correlated with the activation of bitter taste transduction, as well as the regulation of immune balance and inflammatory responses.