Disease-Modifying Anti-rheumatic Drug Prescription Baihu-Guizhi Decoction Attenuates Rheumatoid Arthritis via Suppressing Toll-Like Receptor 4-mediated NLRP3 Inflammasome Activation

Abstract

As a traditional Chinese medicine-originated disease-modifying anti-rheumatic drug prescription, Baihu-Guizhi decoction (BHGZD) is extensively used for the treatment of rheumatoid arthritis (RA) with a satisfying therapeutic efficacy. Mechanically, our previous data indicated that BHGZD may ameliorate RA partially by restoring the balance of the "inflammation-immune" system through regulating the <i>TLR4-c-Fos-IL2-TNF-alpha</i> axis. Toll-like receptor 4 (TLR4) has been revealed to be involved in the activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome complex. Thus, the aim of the current study was to determine the regulatory effects of BHGZD on the TLR4-mediated inflammasome activation during RA progression based on the modified adjuvant-induced arthritis model (AIA-M) and the lipopolysaccharide/adenosine triphosphate (LPS/ATP)-induced pyroptosis cellular models. As a result, oral administration of BHGZD exhibited prominent improvement in the disease severity of AIA-M rats, such as reducing the redness and swelling of joints, arthritis incidence, arthritic scores, and diameter of the limb and increasing pain thresholds. In line with the <i>in vivo</i> findings, BHGZD treatment effectively inhibited the LPS/ATP-induced pyroptosis of both Raw264.7 macrophage and MH7A cells <i>in vitro</i> by reducing pyroptotic cell death morphology (swollen cells) and decreasing propidium iodide-positive and terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL)-positive cells. Notably, the increased expression levels of TLR4, NLRP3, interleukin 1β, and interleukin 18 proteins and the elevated activities of caspase-1 and lactic dehydrogenase in <i>in vivo</i> and <i>in vitro</i> disease models were markedly reversed by the treatment with BHGZD. In conclusion, the above findings proved the immunomodulatory and anti-inflammatory activities of BHGZD, especially in pyroptosis, which may be attributed to the activation of TLR4-mediated NLRP3 inflammasome signaling.