Study On Therapeutic Mechanism Of Dexamethasone And Its Thermosensitive Hydrogel On CIA Rats

Objective: To study the effect of dexamethasone(DEX)and its thermosensitive hydrogel(DLTH)on collagen-induced arthritis rats(CIA),and to explore the pharmacological mechanism.Contents: CIA models were established on Wistar rats.Two different administration routes,frequency and dosage forms:(1)intraperitoneal injection of DEX solution and(2)intra-articular injection of DLTH,were used to observe the therapeutic effect of DEX on joint inflammation,pain and the improvement of overall immune function.Methods:(1)Male Wistar rats were randomly divided into 3 groups:normal group,model group and DEX group.After CIA models were established,DEX group was given injection of dexamethasone(1 mg/kg)intraperitoneally.Dosing frequency: 3 times a week for 4 weeks.(2)Male Wistar rats were randomly divided into normal group,model group and DLTH group.After the CIA rats’ toes swelled,the DLTH group was given40μl DLTH(1mg/kg)injection on each side of knee joints.Frequency: twice a week for 3 weeks.During the experiment,the rats’ body weight,paw volume,articular index were recorded,and mechanical withdrawal threshold(MWT)and pressure pain threshold(PPT)were measured.Finally,we obtained serum,spleen,synovium,cartilage,L4-L6 bilateral dorsal root ganglia(DRG),and knee joints.Detect the changes in serum cytokines,synovial inflammatory factorskey protein levels in the NF-κB pathway,metalloproteinase levels in cartilage,and cartilage immunohistochemistry,combined with knee joint pathology and paw swelling treatment to study the effects of drugs on anti-inflammatory.Compare the changes in the levels of inflammatory factors,nerve factors,ion channels,and serum prostaglandins in DRG between model group and administration group,combined with the change trend of mechanical pain threshold,to explore the drug mechanism on pain relief.Compare the index of immune organs between model group and administration group and then detect inflammatory factors,transcription factor levels,and Th1/Th2 Th17/Treg ratios in splenic lymphocytes to verify the immunomodulatory effect of the drug on the CIA model.The effects of the two dosage forms on the blood concentration were compared by HPLC.Results:1 Intraperitoneal injection of dexamethasone solution(DEX)reduces the pro-inflammatory factors TNF-α,IL-1β,IL-6,and IL-17 in the synovial tissue;regulates cytokines in the serum to.;reduces MMP-9,MMP-13,ADAMTS-4,ADAMTS-5 in the cartilage to inhibits synovial inflammation,inhibit the degradation of the cartilage and improve the body’s anti-inflammatory state.Secondly,it can inhibite the levels of inflammatory factors(TNF-α,IL-1β,IL-6 and IL-17)in DRG,pain-related ion channel receptor TRPV1 and nerve growth-related factors NGF,NPY,and BDNF to increase the levels of CIA rats pain threshold;reduce mechanical hyperalgesia,and relieve pain.In terms of immunity,it can reduce inflammatory factors(TNF-α,IL-1β,IL-6,IL-17)in splenic lymphocytes,improve Th1,Th2,Th17 and Treg specific transcription factors T-bet,GATA3,RORγT,Foxp3 level,adjust the ratio of Th1/Th2,Th17/Treg in the body to improve the immune response of the spleen.2 Intra-articular injection of DLTH can reduce the inflammatory factors in the synovial tissue,reduce the phosphorylation of NF-κB pathway in the synovial tissue,improve the inflammatory pathological state of the synovium,blood vessels,and cartilage of the knee joint.It can reduce the paw volume,arthritis score,eliminate swelling and deformation of the feet,and relieve local inflammation of joints.In terms of pain: by inhibiting IL-6,TNF-α,nerve growth factor NPY,NGF,BDNF in the dorsal root ganglia.It improves the levels of ion channels TRPV1,Nav1.3,Nav1.7,and reduces serum prostaglandins PGE2,PGI2 and increases the content of anti-inflammatory PGD2,and also reduces synovial NGF expression,lower the pain threshold of MWT and PPT in rats to inhibit pain.DLTH can also reduce spleen and thymus enlargement,and improve overall immune function.Conclusions:1 DEX can improve the overall inflammatory state of CIA rats,reduce synovial inflammatory infiltration and cartilage destruction,inhibit pain,and improve overall immune imbalance.2 DLTH can improve CIA synovial hyperplasia,relieve pain by reducing pain-related factors in serum,DRG and synovium,and reduce the organ index of immune organs.Compared with DEX,DLTH can reduce the frequency of administration.