Objective To observe the effect of electroacupuncture(EA) on pyroptosis-related proteins in synovium of knee joint in rats with knee osteoarthritis(KOA)

in order to explore its mechanism underlying improvement of KOA.Methods Forty male SD rats were randomly divided into control

model

EA and medication groups

with 10 rats in each group. The KOA model was established by injecting 0.2 mL 4% papain solution into the right intra-articular cavity

followed by repeating the injection again on day 4 and 7 after the first injection. After successful modeling

rats of the EA group received EA stimulation of “Neixiyan”(EX-LE4) and “Dubi”(ST35) on the right limb for 15 min

once every day

6 days per week

for a total of 4 weeks

and those of the medication group received gavage of celecoxib 24 mg/kg

once every day

6 days per week

for a total of 4 weeks. The severity of dysfunction of the right knee was assessed by using Lequesne's score. Serum interleukin(IL)-1β and IL-18 contents were detected by ELISA. Histopathological changes of the synovium tissue of the right knee joint were observed to give score(synovial pathological score) after H.E. staining. The expression position and intensity of Nod-like receptor pyrin domain 3(NLRP3) in syno-vial tissue were observed by immunohistochemistry. The expression levels of NLRP3

apoptosis-associated speck-like protein containing card(ASC)

Caspase-1

Gasdermin D(GSDMD)

IL-1β and IL-18 mRNAs and proteins(including GSDMD-N) in the synovial tissue of the right knee joint were detected by real-time fluorescence quantitative PCR and Western blot

separately. Results Compared with the control group

the model group had a significant increase in the Lequesne's score

synovial pathological score

serum IL-1β and IL-18 contents

and the expression levels of NLRP3

ASC

Caspase-1

GSDMD

IL-1β

IL-18 mRNAs and proteins and GSDMD-N protein(P<0.01). Whereas relevant to the model group

both the EA and medication groups had marked lower levels of Lequesne's score and synovial pathological score

serum IL-1β and IL-18 contents

and expression levels of NLRP3

ASC

Caspase-1

IL-1β

IL-18 mRNAs and proteins

GSDMD mRNA and GSDMD-N protein(P<0.01

P<0.05). Comparison between two intervention groups showed that the contents of serum IL-1β and IL-18

and the expression levels of IL-1β mRNA and protein were significantly higher in the EA group than in the medication group(P<0.05

P<0.01). No significant differences were found between the EA and medication groups in the Lequesne's score

synovial pathological score

NLRP3

ASC

Caspase-1 and IL-18 mRNAs and proteins

as well as GSDMD mRNA(P>0.05). Conclusion EA can alleviate the inflammatory response of synovial tissues of knee joints in KOA rats

which may be related to its function in down-regulating the expression levels of synovial NLRP3

ASC

Caspase-1

IL-1β and IL-18 mRNAs and proteins

and GSDMD mRNA and GSDMD-N proteins

reducing the occurrence of pyroptosis.