Buzhong Yiqi decoction improves inflammation and oxidative damage in autoimmune thyroiditis by inhibiting apoptosis via the SIRT1-Mediated Nrf2/NF-κB axis.

ETHNOPHARMACOLOGICAL RELEVANCE

Buzhong Yiqi decoction (BZYQ), a compound formula comprising eight traditional Chinese medicinal herbs, has been used clinically to treat various autoimmune diseases, including autoimmune thyroiditis (AIT). Our long-term clinical practice and research have shown that BZYQ demonstrates promising anti-inflammatory efficacy in the management of AIT, and the underlying pharmacological mechanisms involved warrant further exploration.

AIM

To investigate the therapeutic effects and underlying mechanisms of the impact of BZYQ on AIT both in vitro and in vivo.

MATERIALS AND METHODS

An AIT model was developed in NOD.H-2 mice by administering 0.05 % NaI. The therapeutic efficacy of BZYQ on AIT was evaluated using hematoxylin-eosin (H&E) staining and enzyme-linked immunosorbent assay(ELISA). Oxidative stress and inflammation-related parameters, including superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were analyzed. Thyroid cell apoptosis was observed using TUNEL staining. Reverse transcription-quantitative polymerase chain reaction(RT-qPCR), Western blotting, immunohistochemistry, and immunofluorescence were performed. These techniques were used to determine the alterations in key genes and proteins involved in the sirtuin 1 (SIRT1)-mediated Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/nuclear factor-kappaB p65 (NF-κB p65) axis regulating the apoptotic pathway in thyroid tissues of AIT mice after BZYQ intervention. Furthermore, lipopolysaccharide(LPS)was used to create a cellular model, which was then treated with BZYQ-containing serum. Confirmatory studies were conducted using a SIRT1 inhibitor. The protein levels of SIRT1, Nrf2, NF-κB p65, and Caspase-3 in Nthy-ori 3-1 cells were analyzed to gain further mechanistic insights.

RESULTS

BZYQ ameliorated thyroid pathology in AIT mice, reduced inflammatory cell infiltration, lowered inflammation scores, decreased serum levels of TGAb and TPOAb antibodies, and diminished the spleen index. These findings suggest that BZYQ has a protective effect against thyroid damage in AIT. BZYQ-M exhibited the most pronounced therapeutic efficacy. Mechanistically, BZYQ exerted its anti-inflammatory, antioxidant, and antiapoptotic effects by upregulating SIRT1, which subsequently promoted Nrf2 expression and inhibited NF-κB p65 activation. These changes led to altered protein expression and mRNA levels of its downstream targets, considerably suppressing the production of inflammatory cytokines (TNF-α and IL-6), attenuating oxidative stress (MDA, SOD, and CAT), regulating the expressions of apoptotic markers (Bax, Bcl-2, CytC, and Caspase-3), and reducing the apoptosis rate of thyroid cells. Further validation via in vitro experiments revealed that SIRT1 inhibitors can block the protective effects of BZYQ on the Sirt1-mediated Nrf2/NF-κB axis and cellular apoptosis.

CONCLUSION

The findings from this study establish that BZYQ exhibits potent antioxidant and anti-inflammatory activities via the SIRT1-mediated Nrf2/NF-κB p65 axis, reducing thyroid cell apoptosis. These observations unveil a novel mechanism and support the potential of BZYQ as a promising therapeutic agent for AIT.