Effects of electroacupuncture at “Hegu” (LI4) and “Quchi” (LI11) on Parthanatos in atopic dermatitis mice by regulating the PAR2/TRPV3 pathway

To observe the effect of electroacupuncture (EA) at “Hegu” (LI4) and “Quchi” (LI11) on skin inflammatory injury, itching, and poly(ADP-ribose) polymerase 1 (PARP1)-dependent cell death (Parthanatos) in mice with atopic dermatitis (AD) based on the protease-activated receptor 2 (PAR2)/transient receptor potential vanilloid 3 (TRPV3) pathway, and to explore the possible mechanism of EA in the treatment of AD.

Thirty-six male BALB/c mice were randomly divided into a normal group, a model group, and an EA group, with 12 mice in each group. The AD model was established by topical application of calcipotriol (MC903) solution. After successful modeling, the EA group received EA at bilateral LI4 and LI11 once daily, 30 min per session, for 7 consecutive days. The scoring atopic dermatitis (SCORAD) index and scratching frequency were recorded before and after intervention in each group. Histopathological morphology of skin tissue was observed by HE staining. Cell apoptosis in skin tissue was detected by TUNEL assay. The protein expressions of PAR2, TRPV3, interleukin (IL)-33, IL-31, IL-13, PARP1, mitochondrial apoptosis-inducing factor 1 (AIFM1), and macrophage migration inhibitory factor (MIF) in skin tissue were measured by Western blot. The mRNA expression levels of PAR2, TRPV3, inflammatory factors (IL-33, IL-31, IL-13), and Parthanatos-related genes (PAR2, TRPV3, PARP1, AIFM1, MIF) in skin tissue were detected by real-time quantitative PCR. The expression of PARP1 in skin tissue was determined by immunofluorescence.

Compared with the normal group, the model group showed significantly increased SCORAD score (P<0.01), elevated scratching frequency (P<0.01), higher skin cell apoptosis rate (P<0.01), up-regulated protein and mRNA expressions of PAR2, TRPV3, inflammatory factors (IL-33, IL-31, IL-13), and Parthanatos-related factors PARP1, AIFM1, MIF (P<0.01, P<0.05), as well as enhanced PARP1 fluorescence intensity (P<0.01). Compared with the model group, the EA group exhibited decreased SCORAD score (P<0.01), reduced scratching frequency (P<0.01), lower skin cell apoptosis rate (P<0.01), down-regulated protein and mRNA expressions of PAR2, TRPV3, inflammatory factors (IL-33, IL-31, IL-13), and Parthanatos-related factors PARP1, AIFM1, MIF (P<0.05, P<0.01), and weakened PARP1 fluorescence intensity (P<0.01). HE staining showed severe skin lesions, marked epidermal hyperplasia and massive inflammatory cell infiltration in the model group, whereas the EA group displayed relatively intact epidermal structure, significantly alleviated structural damage, and less inflammatory cell infiltration.

EA at LI4 and LI11 can alleviate skin inflammatory injury and itching in AD mice, and its mechanism may be related to down-regulating the PAR2/TRPV3 pathway and inhibiting Parthanatos in skin cells.