Prunella vulgaris L. has been a traditional Chinese anti-inflammatory medicine for hundreds of years. However, clinic evidence indicates that it also causes a cluster of metabolic syndromes such as reduced appetite, diabetes, diarrhea etc. To date, the mechanisms of the anti-inflammation and associated symptoms by P. vulgaris treatment remain unclear.
Network pharmacology studies using TCMSP and Genecards database, Cytoscape, GO and KEGG were applied to reveal the ingredients, hub molecules and their interactions, and enriched biologic processes associated with analgesic and glucose intolerance. Some active gradients and target genes were obtained from the comparisons of relevant databases in TCMSP and Genecards. Connections of validated and predicted gradients, target genes and diseases were visualized through Cytoscape. GO and KEGG were applied to identify the significantly engaged hub genes, biological processes and signaling pathways. To further validate GC and BDNF effects, C57BL/6J male mice were randomly divided into 5 groups, control (C), dexamethasone (Dex, 1 mg/kg/day), PE-treated (35mg, 70mg), and PE (70mg) + mifepristone (2.5 mg/kg/day) (PEM group). Mice were pretreated by water extract of P. vulgaris spica (PE) for 3-4 weeks followed by one of the following tests: acetic acid-induced writhing, hot plate test, rotaroad test, food intake, glucose tolerance test (GTT). Quantitative PCR was applied to detect hepatic and hypothalamic gene expression. Plasma brain-derived neurotrophic factor (BDNF), glucocorticoids, IL1β, IL6 and IL10 were measured by ELISA.
Network pharmacology studies revealed that BDNF, GCs and GC-responsive or down-stream genes such as GC-induced leucine zipper protein (GILZ), glucose-6-phosphatase catalytic subunit 1, protein kinase B (PKB), etc. were intensively involved into anti-inflammation and glucose intolerance. Acetic acid-induced writhing and hot plate tests confirmed the peripheral and central analgesic effects of PE treatment. Based on the results of feeding behavior tests, 4-week PE treatment impeded food intake but increased the ratio of bodyweight gain to food intake. GTT revealed PE treatment impaired glucose disposal in mice. Finally, real time PCR confirmed that hepatic GC-target genes, such as G6Pase, GILZ, SGK1, PKB were up-regulated, and hypothalamic neuropeptide Y (NPY) and agouti-related protein (AGRP) expression were decreased by PE administration. Glycogen synthase kinase 3 beta (Gsk3 β) was mildly increased. Hypothalamic BDNF was up-regulated, whereas hepatic BDNF was down-regulated. Plasma BDNF and GCs were increased, and IL1β, IL6 and IL10 were decreased by PE treatments (p<0.05).
GCs, BDNF, SGK1, insulin and PKB are most relevant molecules to analgesic and glucose intolerance when P. vulgaris is applied. PE treatment plays the analgesic role through the GC, GILZ and PKB regulatory pathways, and regulates the levels of some pro-inflammatory cytokines. Meanwhile, it upregulates G6PC1and GSK3β expression to increase plasma glucose level leading glucose intolerance. Although PE treatment decreases food intake, it makes mice to be prone to obesity. The corresponding increase of plasma BDNF may act as a counterpart to GC effects leading animals to adapt environments more easily.