| Canine atopic dermatitis(CAD)is a type of skin disease in dogs characterized by itching and dermatitis.Its pathogenesis is complex and has a genetic tendency,making it difficult to cure and seriously affecting the quality of life of dogs.Clinically,immunosuppressants such as glucocorticoids(GC)are commonly used to relieve CAD.However,long-term use of these drugs can lead to adverse reactions such as metabolic disorders and immune suppression.Olatinib is a new type of JAK inhibitor with fewer side effects,but it is expensive and easy to develop drug resistance after long-term use.Therefore,finding safer and more effective drugs is an urgent problem to be solved in CAD treatment.Natural compounds such as resveratrol,psoralen,luteolin,magnolol,and asiaticoside have high safety and few side effects.They exhibit various biological activities such as anti-inflammatory and antioxidant effects,and can effectively treat various skin diseases in humans(such as atopic dermatitis AD).However,their effectiveness in treating CAD remains unknown.In order to screen for drugs with therapeutic value for CAD among the above five drugs,the following experiments were carried out in this study:(1)Evaluation of the effect of natural compounds on AD in miceBased on the substitution principle of animal welfare,this study first evaluated the therapeutic effects of five natural compounds in a mouse AD model.The mouse model of AD was established by topically applying 2,4-dinitrochlorobenzene(DNCB)on the skin surface.The AD mice were divided into six groups(n=6)and were orally administered different drugs(resveratrol,osteoline,luteolin,magnolol,and asiaticoside)or solvent(1% carboxymethyl cellulose sodium)once a day.Skin lesions of each group of mice were observed and recorded for 21 days.At the end of the experiment,skin and spleen tissues were collected from each group of mice at the modeling site,and tissue pathological changes were detected through H&E staining.RT-PCR was used to determine the m RNA expression of the inflammatory factors,IL-4,IL-5,and IL-13,to evaluate the therapeutic effect of different natural compounds on AD in mice.The results showed that compared with the model group,the skin lesion score and spleen index of mice in the resveratrol,psoralen,luteolin,magnolol,and asiaticoside groups were significantly reduced to varying degrees,with the resveratrol group showing the most significant reduction.(P<0.05).H&E staining of mouse skin showed that resveratrol could inhibit DNCB-induced epidermal thickening and dermal inflammatory cell infiltration.RT-PCR results showed that compared with the control group,IL-4,IL-5,and IL-13 m RNA expression levels were elevated in both the model group and the resveratrol group mice(P<0.05),while the inflammatory factor expression level in the resveratrol group was significantly lower than that in the model group(P<0.05).In conclusion,resveratrol can significantly inhibit AD-like lesions in mice and relieve skin inflammation.(2)The therapeutic effect of resveratrol on canine atopic dermatitis modelsThese results indicate that resveratrol has a good therapeutic effect on AD in mice,so this experiment further studied its therapeutic effect on CAD models.Twelve healthy beagle dogs were selected,with model group dogs receiving subcutaneous injection and skin patching with DNCB to induce CAD,while control group dogs received injection and patching with the same volume of DNCB control solution.The AD dogs were divided into two groups(n=4),and orally administered with either 1%sodium carboxymethylcellulose or resveratrol solution for 14 consecutive days.The skin lesions and itching were recorded and scored in both groups of experimental dogs.Blood and skin samples were collected from each group of dogs at 24 hours after patching and 14 days after administration for the detection of routine blood tests,biochemical tests,histological examination using H&E staining,and determination of inflammatory factors expression in skin tissues using RT-PCR.The therapeutic effect of resveratrol on CAD was evaluated comprehensively.The results are as follows:(1)After patching,both the model group and drug group of dogs had significantly higher skin lesion and itching scores than the control group(P<0.01).However,after continuous administration for 7 and 9 days,the skin lesion scores of the drug group were significantly lower than those of the model group(P<0.05),and after continuous administration for 9 days,the skin itching scores of the drug group were significantly lower than those of the model group(P<0.05).(2)The results of routine blood tests in dogs showed that at 24 hours after patching and 14 days after drug administration,all indicators of the control,model,and drug groups were within the normal range with no significant differences.(3)Biochemical results in dogs showed that compared with the control group,GLU,CRP in the model group,and CRP in the drug group were significantly increased at 24 hours after patching(P<0.05),and ALB in the drug group was significantly decreased(P<0.05);compared with the model group,there were no significant differences in various indicators of the drug group at 24 hours after patching,and CRP in the drug group decreased after14 days of drug administration.(4)Histological results of H&E staining of canine skin showed that after 24 hours of patching,the stratum corneum of the skin in the model group and the drug group dogs was loose or even detached,the arrangement of the epidermal cell was irregular,the epidermis was separated from the dermis,and a large number of inflammatory cells infiltrated into the dermis.After 14 days of drug administration,the epidermis in the model group thickened,and a large number of inflammatory cells infiltrated into the dermis.In the drug group,the degree of epidermal thickening improved,the arrangement of epidermal cells was regular,and the infiltration of inflammatory cells into the dermis was significantly reduced.(5)The results of RT-PCR analysis of inflammatory cytokines showed that the m RNA expression levels of IL-4,IL-6,and IL-13 in skin tissues of the model group dogs were significantly increased(P<0.05),but their expression levels in the drug group were significantly lower than those in the model group(P<0.05).The above study indicated that compared to psoralen,luteolin,magnolol,and asiaticoside,resveratrol had better therapeutic effects on AD in mice.In addition,resveratrol has high safety and can significantly alleviate the clinical symptoms of CAD,inhibit skin inflammation,and has a certain degree of therapeutic effect on CAD.This study provides a reference for the search for alternative or complementary drugs for CAD. |
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